I recently switched companies and therefore my Java hat to a C# hat. The quality and information these videos provide is insane. Keep up the good work!
Tim, you have completely changed the way I look at Delegates. The tutorial was easy to understand and I can't thank you enough for the kind of example that you picked up. I have went over numerous videos on this topic and I'm relatively new to C# but your presentation skills were so to the point that I was able to bridge the gap pretty easily. Please continue making great tutorials like these! I kept on running from delegates before watching this video
Hi Tim, just let you know that your lessons are becoming an important part of my life, I spend 2 or 3 hrs on listening to them and I love them. Thank you!
Very good explanation. The conclusion for me (in this concrete case): 1. GenerateTotal can send "messages" to Main while it process its work. 2. I can write the code for some operation GenerateTotal does. So GenerateTotal is just a plan, what have to do, but the concrete code is mine.
This is for me: Example: 1:50 What is a delegate?: 7:52 Func delegate: 18:19 Question: 30:55 Action delegate: 34:00 In line delegates (on the fly): 38:04 WinForm UI: 49:22 WinForm UI with In line delegates: 58:37 Ignoring Action delegate: 1:00:52 When using delegates?: 1:02:15
Just want to let you know that if you go to around 50 minutes in the video, you seem to repeat a section where you present the startup code, like if you notice that you already had a private static void already written. I think you forgot to edit it out! Just want to let you know, because looking at the quality of your videos, it shows that you put a lot of time in it and that I put the time to watch it very carefully! Great... Great content, thanks for sharing!
I recomend to move the CalculateMethod to the Library project rather than implementing it in Console and WinForm projects. But thanks for the class. It is awesome I learned a lot
I would suggest doing a video about delegates vs interfaces and when to use each one. I have actually found many cases where doing interfaces caused overflow errors but delegates did not. Does that mean that interfaces are completely useless and a person should always do delegates. Would like to know the advantages and disadvantages of interfaces vs delegates.
Delegates and interfaces aren't really comparable items. Interfaces are just contracts that say that a class will do whatever the contract specifies. This allows us to work with classes that otherwise have no relationship. For instance, you can apply an IDisposable on any class and use it in a "using" statement to properly close out the resources at the end. Those classes can be anything and yet they can all be properly closed out. Quite frankly, Interfaces are probably the most important thing in C#. Without them, there is little point to dependency injection, unit testing is practically impossible (or at least miserable), and code in general becomes much more difficult to manage. I find myself using delegates (beyond events) rarely in my code. I use Interfaces all of the time.
Hi Tim. Well, after months since the first time I watched this, I came back to watch it again. There are points in your course that could be easily missed unless someone came across with in real world. I'm getting used to the delegates (Func and Action actually) when starting separating some codes into libraries. You mentioned the interface at the beginning of this video. I think both interface and delegate are sort of concepts which a programmer need change his/her mindset. I don’t know; however, I believe their application in a code is a big step getting away from classic programming style, otherwise something always whispers in the ears what is the point of using them when things can be done without them. (a false statement of course :) )? Thank you again.
Couple factors here that make things hard for newer developers especially. First, it is a confusing name. The name doesn't make the topic clearer. Second, it involves executing code elsewhere, not inline. That makes it harder to read. Hopefully this video cleared some things up.
0:00 - Intro 1:28 - Demo application walk through 7:52 - Explaining and creating a Delegate 18:19 - Func and Action: problems you can solve with delegates 21:37 - Func Delegate: creating and explaining 30:56 - Why to have delegate, if all the work is done elsewhere 34:00 - Action Delegate: creating and explaining 38:07 - Creating anonymous methods: anonymous Delegate 43:08 - Creating anonymous methods: anonymous Func 45:15 - Creating anonymous methods: anonymous Action 49:30 - Using Delegates in other projects: WinForms 58:37 - Using Anonymous Delegates in other projects: WinForms 1:02:15 - Summary
It would be really helpful if you could make a video about abstract classes. So far you have only covered interfaces and it would help to clear the confusion when it's better to use an interface or an abstract class.
Good voice, pace, etc., and very glad you are here. This video should be reshot posthaste. The use of excruciatingly awkward method names and nonsensical calculations make it hard to track and remember what one has learned. While I got, because of previous experience, the gist of the advantages of delegate usage (console vs. WinForm output is a good example) and delegate usage is an elevated (and intrinsically cryptic-looking) textbookish technique, the user may ask, "Rather than the oddball gymnastics of delegates, why not use an abundantly clear IF statement that branches on console or UI?" The takeaway on FUNC and ACTION was lost. Why would I bother with these? What are they wrapping? Is Santa still coming? Totally lost.
The issue of delegates is who creates the method. The examples I gave with WinForm vs Console illustrate it but they would not be solved with a simple if statement. If you tried an if statement, it would work until you tried to use the library in ASP.NET MVC. Then you would have to update the library and redistribute it again with new logic for that UI. Then you would have to do it again for ASP.NET Core or Xamarin or any other UI. By using a delegate, we can put in the UI logic into a class library that does not change. When we add the UI, we add the UI logic. That allows us to follow the Open Closed Principle (OCP) and it allows us to more easily maintain our library and our applications.
P.S. I listened again to the FUNC and ACTION portion, and I think I get it now. First run through, the naming was throwing me off. Rinse, lather, repeat. :-)
So basically Delegates we use to get parameters for our method right????...... BTW thank you Tim you are just amazing ....from this one video I mastered delegates.
Tim, when i use C2, i get the thing a bit differnet. like as of now 17:10 i get an output like The subtotal is ? 22.93 The total for the cart is ? 20.64 i am not getting the dollar symbol. Why does that happen? How to overcome it?
Still a bit confused. I think a better example will be needed since I still can't grasp the purpose. The interfaces video was perfect. I understood immediately whey it was useful.
Delegates are hard to grasp, especially since we don't often create them until we are creating complex code. The easiest form of delegate to understand (and the most common) is Events. I have a video on them. Check it out. Maybe that explanation will help clear things up.
„Action MyDelegate“ is just a predefined shortcut of „public delegate VOID MyDelegate“ Notice that both don’t return anything. You actually want to avoid a returntype of void (ha ha...), except for events, and use Func instead, which always returns something. There is also a Predicate for Boolean expressions. I recommend to read the official exam ref c# book by Microsoft, it explains all of that, and much more about the language itself, very clear on about 450 pages.
Wonderful video as usual. I have a question. I have seen in some tutorials using delegate to attach more than one method in it. what is the real time use of it?
@@IAmTimCorey public delegate void MyDelegate(); private void Method1() { Console.WriteLine("Method1 invoked"); } private void Method2() { Console.WriteLine("Method2 invoked"); } private void button_Click(object sender, EventArgs e) { MyDelegate myptr = null; myptr += this.Method1; myptr += this.Method1; myptr.Invoke(); } What is the use of this kind of assignment in real programming?
If you wanted to have 0 or more methods fired when something happened. For instance, this is how events work. You might have multiple methods being fired when an event happens.
Will we be seeing more videos? Also, do you ever put methods in the models of the library to run the SqlConnector commands? It seems like it would make sense to have get and save methods on the library classes.
I'm going to be putting out new videos soon. I've had some health issues (I'll be doing a video on this too) that have taken a lot out of me. I'm starting to recover now and I can't wait to start getting videos on here again. As for your other question, I'm not sure I'm visualizing what you want to do here. Are you saying to put a get and save method on the model itself? The problem with that would be if you ever wanted to change database types. You would need to change every model.
@@IAmTimCorey worth the waiting You video always have good example show all the features of the library Sadly some of the video still in dotnet framework, hope you have time update them to dotnet core. Like dependency injection
For the most part, it doesn't matter that it is .NET Framework vs .NET Core for my videos. DI still works the same (maybe slightly different where you set it up but the same in how you set it up) in .NET Core. I will try to cover some differences in various topics, though.
Also, i could not find the video that showed delegates with async. Is there a special video that shows how to do delegates with async. Because that is actually very common. For example, with the example you showed with windows forms. if you used the same example with xamarin forms, then you have to do await because their messagebox requires await otherwise, it runs the rest of the code even though a person did not click the messagebox which causes all kinds of problems. Its also possible that background tasks has to do delegates that need to be thread safe as well.
Why did you put the delegate inside the class rather than the more general namespace? Can a delegate be accessed from anywhere in a solution meaning it has unlimited scope. Did you need to declare references from the UI project to the demo library?
(I'll share what happens practically - the theory is a bit more complex) A delegate shares an access point to the code you point at so that the method you send it to can call the code you send it. You don't need to give the caller access to the namespace or library where the code it is calling lives. Remember an event is a type of delegate. For events, we tell it which method to call internally even if the event is fired in an external class. The reason this works is because we basically pass a message (with the associated data) to every indicated location. At that location, the correct method gets called.
I recommend reading the doc about Delegates and doing some basic examples that MS has in their docs. Then come back and watch the video, it will make more sense.
Hi Tim - is there a problem with the code in the download? When I open the DelegatesDemo.sln (for DelegatesDemo-Start), it does not match the code are showing at the beginning. For example, the GenerateTotal() method only has a single line which throws a not implemented exception. The Main method doesn’t have the line which writes out the total (immediately after the PopulateCartWithDemoData call.) Am I looking at the wrong code?
I understanad everything about delegates but when i want to use it on simple project on wfa with 2 forms i dont know how to do that.Its not hard to understand but it is hard to implement it
My recommendation is to start by building a few practice apps that use delegates. Don't make them "do" anything. Just have them use delegates so you get more comfortable with how they work and how to implement them in a fresh application.
Hi Tim! I lost my links where I saved your content at my Company Favorites. Don't have them anymore. I worked on "CMDemo" and "WPFDemo" which I believe were from you. If so can you point me towards these videos? Both are for WPF
I just started watching to find out about delegates but the assumed knowledge of LINQ and Lamda expressions puts it beyond me. Maybe I'll be back after learning about those.
This is incoherent to me (complete beginner to delegates). I keep hearing you refer to delegates as methods and i dont understand why when they are parameters passed in a method as a delegate type.
That's correct. Delegates are methods that are passed around like parameters so that the method you pass them into can call the passed in delegate whenever they want.
@Michael Blair If I understand what I've learned from this video, the concept of delegates is simple, merely the setup is intimidating. The primary idea is displayed in this video if you ignore the other fluff. Once you understand the primary idea, the fluff starts to make more sense. The primary idea is that you are passing methods from one library/program to another library/program. This makes it so that your library, for example, doesn't need to understand what the Console class is, or what it's method WriteLine() does. It can simply delegate (the word delegate, where the second half sounds like the word "gate") that information back to the passed method and let the method perform the instructions that it needs since it already knows what the Console class is and it's methods like WriteLine(). Rather than having 100 using statements and every program/library you ever write needing to understand every intricate detail of everything it interacts with, it can merely delegate that information back to the callee and let them handle it instead. As @IAmTimCorey said, think of the events that are triggered by your mouse and keyboard when you design WinForms/WPF applications with a graphical UI... That textBoxDemo_Click method Tim wrote would be pretty useless since he never calls that method anywhere in his code, but because it is linked up with a System.EventHandler when the Button.Click event is called, now it knows to look inside his code for a method with a matching signature. It finds it, and calls it, every time the button's click method is called. Tim, while this video is a wealth of information, I have to admit, even I am struggling with the concepts in this video. I absolutely think, if you're up to the unfortunate amount of work that comes with it, that you should re-do this video, and start the approach by teaching that primary concept first (how delegates work) using the button events example. I feel like the rest of the content would be easier to digest if the primary concept was taught first. Even if I perfectly took on the information taught, to the best of my ability, I would have to watch this video twice so that the end would make the beginning easier to digest. (I'll probably have to watch this video 5 times, personally, but that is not your fault in any way.)
It's maybe because I'm tired but at: (products, subTotal) => { ... } Where do products and subTotal variable come from? YEah, I kinda got lost towards the end. :/
Those are the names I gave the two parameters. We know the method will have two input parameters (because of the declared signature of the method) so when I create the inline method, I shortcut it by just giving the parameter names because C# knows the rest already. Yep, it is a bit confusing until you think through the fact of what C# already knows. Essentially we are letting C# assume the rest because that is what it has to be. The actual names don't matter to the signature, but they do to the implementation (which is what I'm creating here) so I tell the system what the names will be.
Could someone explain the syntax: {subtotal:C2} subtotal is obviously referring to the value passed in...but what the heck is C2 and where is it coming from?
C2 is a standard formatting command that tells the system to format the number as currency with two decimal points: docs.microsoft.com/en-us/dotnet/standard/base-types/standard-numeric-format-strings
C2 is decimal formatting. You can check out the link find more info social.msdn.microsoft.com/Forums/vstudio/en-US/9f3a11e5-9456-42c0-8437-348e157ba959/c-format-a-decimal?forum=netfxbcl
These things can be oh so easily missused. Please, only use these when they make sense and are really the best way to do things. Otherwise, the poor sucker who comes after you will spend an evening wondering what you where trying to do...
Okay, you are officially the first and only good tutorial I have ever seen on delegates. My issue has always been "Why?". Because I understand what delegates do but never understood why I would go through the trouble of setting them up. This shed light on everything! You're the only one to show how delegates can essentially carry the value of a method and make it transferable to different UI's without having to change very much. Thank you so much for putting the time into these videos! I hope I can be a better developer by using this to my advantage because not even people I work with could give me this explanation.
Agreed, that's the problem with 99% of tutorials about this. They always approach it from the purely technical side of things, basically just "it can do this and this and this", which just makes it confusing and annoying. Only when seeing it implemented and applied to an actual problem a developer may face does it actually "click" and become relevant.
@@roydonk2878 very true, though, that's the problem with most tutorials about any abstract subject. Oddly enough I originally went to college to be a researcher in physics and that sort of issue happens constantly when learning math. "This is what this equations does. Memorize it. Look, *writes out equation and solves it in minutes* its so easy." I really appreciate videos like this and the people who make them because it has become apparent that teaching (like actual teaching) is a skill not everyone can learn. There are lots of "teachers" in the world and yet so few who are actually able to teach. I'm thankful Tim is someone who can actually teach a subject instead of just reading the definition out load.
Its the hardest thing about learning new or advanced areas in coding, is that the simplicity of the example environment, obscures the usefulness of the new tool.
That is where practice helps. Trying out what you are learning can reveal what you missed or what was not taught. Then you know the right questions to ask to go deeper.
Understanding the concept is easy but actually thinking "I could use a delegate for that" while coding, this needs a lot of experience. The problem: as long as you don't use it you will forget it. I'm kinda stuck now.
- The best explanation of Delegate. - The best part of this video is that the focus is on details and that is where the devil lies. - Keep up the good work Tim Corey. :)
This tutorial is better than the one on pluralsight for sure. However, it's still a little confusing having three different types of delegates passed into a single function, especially as a tutorial. I also noticed a few times you mentioned this isn't how we would actually want to do it, which is usually not something you should be showing people who have absolutely no idea what delegates are. I like to learn best practices, and while this isn't a tutorial on best practices, I want to see delegates used in cases where it makes sense to use them, where they are one of the best solutions for a particular problem. I really would have liked to see some cleanup, instead of using 3 delegates, clean it up and just use 1.
He still encompassed the power of delegates and their use if you watch to the end. He mentioned "this isn't how you'd be using delegates" as a preface to saying he was over using them to show the different types. Stop relying on him and use your programmer mind. How would you condense it into 1? Its easy, all those delegates can actually be made into one single function and delegate. You can do the whole calculation, and message alerts, using one method, and pass that single method to a delegate that returns what you need. He just extrapolated it into the different types for educative purposes. It doesn't mean it isn't the proper way to use delegates. This is still the proper way. If you watched the WinUI section of the video, you will see how convenient those delegates ended up being. You can run code in classes completely unrelated and have it compile and work.
Most of the videos does not explain the concept, and they just start coding. Delegates provide ability to pass methods as parameters to other methods. So that other methods can execute them. In Javascript functions are objects. So passing a function as parameter to other methods is not a problem. But in C#, you must add the function reference to a delegate object, and then it can be passed to another method, which can execute it as and when needed. Most popular use of delegates is in implementing callback methods or event handlers. C# EVENTS use delegate internally to implement events and event handlers. The PUBLISHER class declares a delegate, and then an event which uses the delegate internally. Then raises the event as and when needed. The SUBSCRIBER class subscribes to the event of publisher. Internally, it just adds the EventHandler method reference to the delegate of SUBSCRIBER. That is the whole story.
@@IAmTimCorey idk what this commenter's point is either. Most videos over explain mostly on why you should use certain concepts but they fail to show actual coding examples. I like that about your videos. I don't fully understand concepts until I see their application. I appreciate your videos. Also caught you on .NET Rocks
This isn't a beginner video. It is a video for learning delegates for the first time but delegates are an advanced topic. If you want to learn C# in order, check out my Foundation in C# course series at www.iamtimcorey.com/p/complete-foundation-in-c-course-series It will start you from the beginning and take you through to a place where you could be a junior or even mid-level C# developer.
I just realized that there was an editing mistake. The video has near-duplicate sections at 49:58 and at 50:23. Threw me off there for a second. The first duplicate already includes the method "PrintOutDiscountAlert". The second duplicate the "PrintOutDuplicateAlert" is added.
Hi Tim, Excellent video as always! Got a clear picture of delegates. Just one question. When I try to print currency like you did here in video (C2), it's not displaying in the console. Instead, question mark (?) is printing like below. Any suggestions? Example oonsole output --> The subTotal for items in cart 1 is ? 45.42
My brains is exploiting, I understood but I still don’t know how to apply it in my applications, I mean I can change one method in my application but I can also change them all so what’s the limit
I can give you an example of one place we use Func in our application where I work now. Maybe that will help a little. We have a "CacheService" which stores values against a key. The service has one method called "GetOrCreateValue" which takes in a string, which is the key, and a Func. Since we use the cache service in many places in the application, the logic of how we create the value is different everywhere, so that logic can't be added to the cache service. All the cache service does is check in the cache for a value with that key, if it finds it, it returns it. If it doesn't find it then it will run whatever the Func is, then store the value for next time. I can try to explain a little better if this was confusing but I'm hoping a real world example might be useful :)
I think this video was helpful as the title states for a practical demonstration, but not sure if the concepts were explained well enough for someone that is watching that doesn't have a lot of experience using delegates. Although, I do understand that we use Func and Action Delegates all the time without having a sound understanding of what delegates are. Just wondering why you didn't mention anything about Callbacks? Sorry if I was to critical, but I am just trying to get a good understanding of Delegates so I can exploit their full potential. Thanks !!!
A callback is a delegate. It is just another word for it. My recommendation would be to practice what I showed you in the video. That will help give you a firmer grasp on the subject. The problem with delegates/callbacks/actions/events/etc. is that they are a bit complex and there are tons of fancy names being thrown around that makes matters worse instead of better. My remedy is always to get your hands dirty and see what things actually do for yourself. That way, you can have a frame of reference when you are reading confusing terms. I hope that helps. And no, I didn't read that as critical, but thanks for clarifying. I'm glad you are trying to get a good handle on the topic.
@@IAmTimCorey Thanks Mr. Corey for that excellent advice. I got some help from someone that understands Delegates well and they have me up to speed. They said they commonly use them to notify the user that some event has occurred or after a process has completed asynchronously. I am looking for other use cases to apply them as well, actually I want to use them in a scenario where I am using an Interface, I'm thinking the ultimate goal is to exploit both the power of interfaces and delegates together. Thanks !!!
No BS, I watched this video 5 days ago and used my knowledge to answer an in person interview question today!! Thanks Corey!
Awesome! Good luck on landing the job. Glad I could help.
I recently switched companies and therefore my Java hat to a C# hat.
The quality and information these videos provide is insane. Keep up the good work!
Thank you!
Tim, you have completely changed the way I look at Delegates. The tutorial was easy to understand and I can't thank you enough for the kind of example that you picked up. I have went over numerous videos on this topic and I'm relatively new to C# but your presentation skills were so to the point that I was able to bridge the gap pretty easily. Please continue making great tutorials like these! I kept on running from delegates before watching this video
I am glad it was helpful.
Tim Corey is a national treasure. Prove me wrong.
Thanks!
Comparing delegates and interfaces is one of the best explanations I've come across so far.
Glad it was helpful!
This must be the best video on delegates I came across so far.
Great!
The last part that winform was connected to the function that uses delegate was the best part. Thank you for your contribution.
Glad it was helpful!
Finally I have started to understand delegates and their usage. Thanks Tim!!
Awesome!
Hi Tim, just let you know that your lessons are becoming an important part of my life, I spend 2 or 3 hrs on listening to them and I love them. Thank you!
Awesome! I'm glad you are finding them valuable.
this video is the ULITIMATE GOAT! thanks Tim, you did it again.
I am glad it was helpful.
I've read about delegates in Shildt's book, then in Troelson's book and finally only after this amazing tutorial I get it. Thank you so much!
You are welcome.
Another great tutorial. I'm still a little nervous around delegates and anonymous methods, but going through this tutorial helped so much. Thanks Tim.
Glad it helped!
Very good explanation. The conclusion for me (in this concrete case):
1. GenerateTotal can send "messages" to Main while it process its work.
2. I can write the code for some operation GenerateTotal does.
So GenerateTotal is just a plan, what have to do, but the concrete code is mine.
This is for me:
Example: 1:50
What is a delegate?: 7:52
Func delegate: 18:19
Question: 30:55
Action delegate: 34:00
In line delegates (on the fly): 38:04
WinForm UI: 49:22
WinForm UI with In line delegates: 58:37
Ignoring Action delegate: 1:00:52
When using delegates?: 1:02:15
Nice!
nicee
Come back to say Thanks!! I used the knowledge gain here in my actual work today! Very excited!!
Fantastic! I am glad it was helpful.
once again, tim corey had the best video on the topic
Thank you.
Excellent Tim...keep the good work going.
Thanks!
Just want to let you know that if you go to around 50 minutes in the video, you seem to repeat a section where you present the startup code, like if you notice that you already had a private static void already written. I think you forgot to edit it out!
Just want to let you know, because looking at the quality of your videos, it shows that you put a lot of time in it and that I put the time to watch it very carefully!
Great... Great content, thanks for sharing!
That could be and I just missed it when doing my edits. Glad you enjoyed it anyway.
That's an excellent way of teaching. It's much easier to understand like this instead of reading the concept in book. :)
I am glad you are finding it enjoyable.
you're a genius men, seriously! :) I subscribe instantly
Thank you!
Holy fk if i had u as my teacher in school i would have called Bill Gates my employee by now. Keep up the good work.
Thanks!
I recomend to move the CalculateMethod to the Library project rather than implementing it in Console and WinForm projects. But thanks for the class. It is awesome I learned a lot
You are welcome.
I would suggest doing a video about delegates vs interfaces and when to use each one. I have actually found many cases where doing interfaces caused overflow errors but delegates did not. Does that mean that interfaces are completely useless and a person should always do delegates. Would like to know the advantages and disadvantages of interfaces vs delegates.
Delegates and interfaces aren't really comparable items. Interfaces are just contracts that say that a class will do whatever the contract specifies. This allows us to work with classes that otherwise have no relationship. For instance, you can apply an IDisposable on any class and use it in a "using" statement to properly close out the resources at the end. Those classes can be anything and yet they can all be properly closed out. Quite frankly, Interfaces are probably the most important thing in C#. Without them, there is little point to dependency injection, unit testing is practically impossible (or at least miserable), and code in general becomes much more difficult to manage. I find myself using delegates (beyond events) rarely in my code. I use Interfaces all of the time.
Its really "in a nutshell" about delegates. Great stuff 👍
Glad you enjoyed it
I am enjoying even the comments, great discussions here awesome environment. Cnt wait for the next one!!!!
Excellent!
Again, excellent and simply explained. Thank you.
Thank you for investing time with Tim's videos.
Hi Tim. Well, after months since the first time I watched this, I came back to watch it again. There are points in your course that could be easily missed unless someone came across with in real world. I'm getting used to the delegates (Func and Action actually) when starting separating some codes into libraries. You mentioned the interface at the beginning of this video. I think both interface and delegate are sort of concepts which a programmer need change his/her mindset. I don’t know; however, I believe their application in a code is a big step getting away from classic programming style, otherwise something always whispers in the ears what is the point of using them when things can be done without them. (a false statement of course :) )?
Thank you again.
Ah delegates, the worst topic in C# history! Thank you Tim for covering it.
Luigi Zambetti why is it the worst topic?
You make a powerful statement like that, can’t even say why?
Jim Cheseborough They are hard to understand for beginners. Like pointers in C
Luigi Zambetti just think of delegates as actions or "verbs" being treated as nouns or objects that you can pass around like a normal variable
Couple factors here that make things hard for newer developers especially. First, it is a confusing name. The name doesn't make the topic clearer. Second, it involves executing code elsewhere, not inline. That makes it harder to read. Hopefully this video cleared some things up.
0:00 - Intro
1:28 - Demo application walk through
7:52 - Explaining and creating a Delegate
18:19 - Func and Action: problems you can solve with delegates
21:37 - Func Delegate: creating and explaining
30:56 - Why to have delegate, if all the work is done elsewhere
34:00 - Action Delegate: creating and explaining
38:07 - Creating anonymous methods: anonymous Delegate
43:08 - Creating anonymous methods: anonymous Func
45:15 - Creating anonymous methods: anonymous Action
49:30 - Using Delegates in other projects: WinForms
58:37 - Using Anonymous Delegates in other projects: WinForms
1:02:15 - Summary
Thanks! I added it to the description.
@@IAmTimCorey You sure did. Typo and all! lol
Through*
@@DoorThief Thanks. English is not my natural language. I try spellcheck everything thou. I slipped up. Sorry.
It would be really helpful if you could make a video about abstract classes. So far you have only covered interfaces and it would help to clear the confusion when it's better to use an interface or an abstract class.
That is on the schedule to do soon. Good suggestion.
Great video, Tim!
Already subscribed to you blog. I'll take a deeper look into the courses you sell.
Thanks a lot!
You are most welcome. Thanks for watching.
Thank you for this! Im not a native speaker but these tutorials are very easy to follow 👍.
Awesome!
@CloroxBleach then maybe you can explain it to me :)
@CloroxBleach then maybe you can explain it to me :)
You mentioned making a video on async safe delagates....Have you made that video yet, and which one is it?
Not yet!
@@IAmTimCorey Thanks for getting back with me, I will try to be patient!!
I really like doing something with c#.
You are So cool.
Thanks you.
You're very welcome!
Good voice, pace, etc., and very glad you are here.
This video should be reshot posthaste. The use of excruciatingly awkward method names and nonsensical calculations make it hard to track and remember what one has learned.
While I got, because of previous experience, the gist of the advantages of delegate usage (console vs. WinForm output is a good example) and delegate usage is an elevated (and intrinsically cryptic-looking) textbookish technique, the user may ask, "Rather than the oddball gymnastics of delegates, why not use an abundantly clear IF statement that branches on console or UI?"
The takeaway on FUNC and ACTION was lost. Why would I bother with these? What are they wrapping? Is Santa still coming? Totally lost.
The issue of delegates is who creates the method. The examples I gave with WinForm vs Console illustrate it but they would not be solved with a simple if statement. If you tried an if statement, it would work until you tried to use the library in ASP.NET MVC. Then you would have to update the library and redistribute it again with new logic for that UI. Then you would have to do it again for ASP.NET Core or Xamarin or any other UI. By using a delegate, we can put in the UI logic into a class library that does not change. When we add the UI, we add the UI logic. That allows us to follow the Open Closed Principle (OCP) and it allows us to more easily maintain our library and our applications.
Yikes. Well, so much for formatting. :-)
P.S. I listened again to the FUNC and ACTION portion, and I think I get it now. First run through, the naming was throwing me off. Rinse, lather, repeat. :-)
It's very Great Explanation.. wonderful, Thx a lot sir
You are welcome.
At 1:04:35 shouldn't it be "Dashboard inherits from Form" instead of "Form inherits from Dashboard"?
Yes that is clearly what he meant to say
thank you for all your hard work on this
You are welcome.
So basically Delegates we use to get parameters for our method right????...... BTW thank you Tim you are just amazing ....from this one video I mastered delegates.
Tim, when i use C2, i get the thing a bit differnet.
like as of now 17:10 i get an output like
The subtotal is ? 22.93
The total for the cart is ? 20.64
i am not getting the dollar symbol. Why does that happen? How to overcome it?
Still a bit confused. I think a better example will be needed since I still can't grasp the purpose. The interfaces video was perfect. I understood immediately whey it was useful.
Delegates are hard to grasp, especially since we don't often create them until we are creating complex code. The easiest form of delegate to understand (and the most common) is Events. I have a video on them. Check it out. Maybe that explanation will help clear things up.
Me either! I'll watch this video for more times.
@@IAmTimCorey I have never ran into anything in development that was hard to grasp if explained correctly.
Best Teacher Out There 🙏🏻
Thanks!
thanks so much, Tim.
Majestic!
You are welcome.
Was there ever made a video on delegates in asyncronous programming?
Very well explained. However I would add that you are not passing the method itself. You are passing a pointer or a pipeline to the method.
Yep.
So, is there a way to do the same thing but using explicit pointers in C#? I'm just curious.
Good vid, clear and easy to understand, thank you
You are welcome.
what is the difference between an action delegate and a normal delegate?
„Action MyDelegate“
is just a predefined shortcut of
„public delegate VOID MyDelegate“
Notice that both don’t return anything. You actually want to avoid a returntype of void (ha ha...), except for events, and use Func instead, which always returns something. There is also a Predicate for Boolean expressions.
I recommend to read the official exam ref c# book by Microsoft, it explains all of that, and much more about the language itself, very clear on about 450 pages.
Wonderful video as usual. I have a question. I have seen in some tutorials using delegate to attach more than one method in it. what is the real time use of it?
I am not sure what you mean. What are they doing?
@@IAmTimCorey
public delegate void MyDelegate();
private void Method1()
{
Console.WriteLine("Method1 invoked");
}
private void Method2()
{
Console.WriteLine("Method2 invoked");
}
private void button_Click(object sender, EventArgs e)
{
MyDelegate myptr = null;
myptr += this.Method1;
myptr += this.Method1;
myptr.Invoke();
}
What is the use of this kind of assignment in real programming?
If you wanted to have 0 or more methods fired when something happened. For instance, this is how events work. You might have multiple methods being fired when an event happens.
@@IAmTimCorey Noted. Thank you.
Welcome to OO programming ...we fuck things up and then come up with over-complicated solutions to solve them
That's an...interesting take, especially on a video about delegates.
@@IAmTimCorey By the way good job on explaining things 👍
My comment was refering strictly to OO programming not you
What i needed was delegates with events.
Events are delegates. I do have a video on events, if that would help.
Will we be seeing more videos? Also, do you ever put methods in the models of the library to run the SqlConnector commands? It seems like it would make sense to have get and save methods on the library classes.
I'm going to be putting out new videos soon. I've had some health issues (I'll be doing a video on this too) that have taken a lot out of me. I'm starting to recover now and I can't wait to start getting videos on here again.
As for your other question, I'm not sure I'm visualizing what you want to do here. Are you saying to put a get and save method on the model itself? The problem with that would be if you ever wanted to change database types. You would need to change every model.
link to the source code is dead....
I updated it. It should work now.
Tim can you do a video for RealTime library SignalR ?
I will add it to the list. Thanks for the suggestion.
@@IAmTimCorey worth the waiting
You video always have good example show all the features of the library
Sadly some of the video still in dotnet framework, hope you have time update them to dotnet core. Like dependency injection
For the most part, it doesn't matter that it is .NET Framework vs .NET Core for my videos. DI still works the same (maybe slightly different where you set it up but the same in how you set it up) in .NET Core. I will try to cover some differences in various topics, though.
Also, i could not find the video that showed delegates with async. Is there a special video that shows how to do delegates with async. Because that is actually very common. For example, with the example you showed with windows forms. if you used the same example with xamarin forms, then you have to do await because their messagebox requires await otherwise, it runs the rest of the code even though a person did not click the messagebox which causes all kinds of problems. Its also possible that background tasks has to do delegates that need to be thread safe as well.
I will add it to the list. Thanks for the suggestion.
Sorry I don't understand... is there a redundant repetition at 50:00 ? (Edit: Yes I think there is...)
17:39 bookmark where it clicked. I can use a delegate to close out nested winforms, which is what i was trying to do
I am glad you found what you needed.
Only 16 arguments!?! Oh no!!!! It's Y2K all over again! :-) :-) :-)
dosomething( param => callback(param)) is this what delegates seems like?
Why did you put the delegate inside the class rather than the more general namespace? Can a delegate be accessed from anywhere in a solution meaning it has unlimited scope. Did you need to declare references from the UI project to the demo library?
(I'll share what happens practically - the theory is a bit more complex) A delegate shares an access point to the code you point at so that the method you send it to can call the code you send it. You don't need to give the caller access to the namespace or library where the code it is calling lives. Remember an event is a type of delegate. For events, we tell it which method to call internally even if the event is fired in an external class. The reason this works is because we basically pass a message (with the associated data) to every indicated location. At that location, the correct method gets called.
This is super hard to understand
They are an advanced topic, for sure. It helps to practice them. Seeing them work is sometimes easier than trying to abstractly understand them.
I recommend reading the doc about Delegates and doing some basic examples that MS has in their docs. Then come back and watch the video, it will make more sense.
It's funny how as a Javascript user, this is one of the few actually not-so-hard topics for me, considering this is pretty similar to callbacks.
Hi Tim - is there a problem with the code in the download? When I open the DelegatesDemo.sln (for DelegatesDemo-Start), it does not match the code are showing at the beginning. For example, the GenerateTotal() method only has a single line which throws a not implemented exception. The Main method doesn’t have the line which writes out the total (immediately after the PopulateCartWithDemoData call.) Am I looking at the wrong code?
Not sure, sorry.
Yep, it is missing but you can type it out as it is on the video...
Tim, syntax for creating an instance of a delegate is same as that for class, so I'm curious to know is delegate really a class behind the scenes?
I don't know the deep underlying structure. I don't believe so, but I'm not totally sure.
Tim,That is ok
There is a delegate class. But you can't instantiate it or extend it. It can only be used through DELEGATE keyword.
Not exactly, delegates are more like reference type 'variables'
@@jlitodelcid326 but class is also a reference type right?
I understanad everything about delegates but when i want to use it on simple project on wfa with 2 forms i dont know how to do that.Its not hard to understand but it is hard to implement it
My recommendation is to start by building a few practice apps that use delegates. Don't make them "do" anything. Just have them use delegates so you get more comfortable with how they work and how to implement them in a fresh application.
Hi Tim! I lost my links where I saved your content at my Company Favorites. Don't have them anymore. I worked on "CMDemo" and "WPFDemo" which I believe were from you. If so can you point me towards these videos? Both are for WPF
I think those were the first and third videos in this playlist: th-cam.com/play/PLLWMQd6PeGY3QEHCmCWaUKNhmFFdIDxE8.html
@@IAmTimCorey Thanks Again!!
thanks a lot bro
its a great tutorial helped me a lot
wish you all the luck
big fan from Gaza Palestine
I'm glad it was so helpful.
@@IAmTimCorey
i wonder if you cover MVC request life cycle in one of your videos
I just started watching to find out about delegates but the assumed knowledge of LINQ and Lamda expressions puts it beyond me. Maybe I'll be back after learning about those.
I believe you only need to know about lambda expressions, not LINQ too.
@@IAmTimCorey
decimal subTotal = Items.Sum(x => x.Price);
Isn't Sum, in Items.Sum, a LINQ extension to query collections?
Ah, yep, I didn't realize I had that in this video. Although that isn't necessary for delegates.
@@IAmTimCorey
Thanks.
I am trying to fast track a simple understanding of these things so I can look closer at delegates. I'll be back.
Thank you sir
You are welcome.
thank youu, helped a lot
You are welcome.
Good tutorial.
Thanks!
Thanks alot.
You are welcome.
Thank ou so much, I now have better delegates understand.
I am glad it was helpful.
This is incoherent to me (complete beginner to delegates).
I keep hearing you refer to delegates as methods and i dont understand why when they are parameters passed in a method as a delegate type.
That's correct. Delegates are methods that are passed around like parameters so that the method you pass them into can call the passed in delegate whenever they want.
@@IAmTimCorey This helped me alot. I figured it out i belive. update: nevermind, i didn't learn a thing.
@Michael Blair If I understand what I've learned from this video, the concept of delegates is simple, merely the setup is intimidating. The primary idea is displayed in this video if you ignore the other fluff. Once you understand the primary idea, the fluff starts to make more sense. The primary idea is that you are passing methods from one library/program to another library/program. This makes it so that your library, for example, doesn't need to understand what the Console class is, or what it's method WriteLine() does. It can simply delegate (the word delegate, where the second half sounds like the word "gate") that information back to the passed method and let the method perform the instructions that it needs since it already knows what the Console class is and it's methods like WriteLine(). Rather than having 100 using statements and every program/library you ever write needing to understand every intricate detail of everything it interacts with, it can merely delegate that information back to the callee and let them handle it instead.
As @IAmTimCorey said, think of the events that are triggered by your mouse and keyboard when you design WinForms/WPF applications with a graphical UI... That textBoxDemo_Click method Tim wrote would be pretty useless since he never calls that method anywhere in his code, but because it is linked up with a System.EventHandler when the Button.Click event is called, now it knows to look inside his code for a method with a matching signature. It finds it, and calls it, every time the button's click method is called.
Tim, while this video is a wealth of information, I have to admit, even I am struggling with the concepts in this video. I absolutely think, if you're up to the unfortunate amount of work that comes with it, that you should re-do this video, and start the approach by teaching that primary concept first (how delegates work) using the button events example. I feel like the rest of the content would be easier to digest if the primary concept was taught first. Even if I perfectly took on the information taught, to the best of my ability, I would have to watch this video twice so that the end would make the beginning easier to digest. (I'll probably have to watch this video 5 times, personally, but that is not your fault in any way.)
It's maybe because I'm tired but at: (products, subTotal) => { ... } Where do products and subTotal variable come from?
YEah, I kinda got lost towards the end. :/
Those are the names I gave the two parameters. We know the method will have two input parameters (because of the declared signature of the method) so when I create the inline method, I shortcut it by just giving the parameter names because C# knows the rest already. Yep, it is a bit confusing until you think through the fact of what C# already knows. Essentially we are letting C# assume the rest because that is what it has to be. The actual names don't matter to the signature, but they do to the implementation (which is what I'm creating here) so I tell the system what the names will be.
Oh ok, thanks.
@@ZoidbergForPresident this was my breaking point as well. I stared at those inline delegates for a while. But I get it now.
Could someone explain the syntax: {subtotal:C2}
subtotal is obviously referring to the value passed in...but what the heck is C2 and where is it coming from?
C2 is a standard formatting command that tells the system to format the number as currency with two decimal points: docs.microsoft.com/en-us/dotnet/standard/base-types/standard-numeric-format-strings
C2 is decimal formatting.
You can check out the link find more info
social.msdn.microsoft.com/Forums/vstudio/en-US/9f3a11e5-9456-42c0-8437-348e157ba959/c-format-a-decimal?forum=netfxbcl
docs.microsoft.com/en-us/dotnet/standard/base-types/standard-numeric-format-strings?redirectedfrom=MSDN
These things can be oh so easily missused. Please, only use these when they make sense and are really the best way to do things. Otherwise, the poor sucker who comes after you will spend an evening wondering what you where trying to do...
With great power comes great responsibility.
Ohhh sooo
What is "message" at 45:26 plz?
I think it's mentioned because it's from instance "cart" of class: "ShoppingCartModel" where "cart" instance is in the beginning before the dot?
Message is the parameter for the lambda expression that he is using.
(MyVar) => Console.Writeline($"Cart 2 Alert {MyVar}")
SIir Why we Use Delegates Why The are required?
The video talks you through some options of when they are useful. I can't tell you every case, since there are so many possibilities.
@@IAmTimCorey Sir Plz Tell Some Comman Advantages
@@fansban7292 In the first example, you can pass a private function of an object to another class and "access" it, instead of making it public
@@williamgingras304 Thanks
that moment when you've been watching for 40 minutes and he says "in a nutshell" 38:03
lol
You should see the book called "C# 9.0 in a Nutshell" then :) It's > 1000 pages long.
Okay, you are officially the first and only good tutorial I have ever seen on delegates. My issue has always been "Why?". Because I understand what delegates do but never understood why I would go through the trouble of setting them up. This shed light on everything! You're the only one to show how delegates can essentially carry the value of a method and make it transferable to different UI's without having to change very much.
Thank you so much for putting the time into these videos! I hope I can be a better developer by using this to my advantage because not even people I work with could give me this explanation.
Glad it was helpful!
Agreed, that's the problem with 99% of tutorials about this. They always approach it from the purely technical side of things, basically just "it can do this and this and this", which just makes it confusing and annoying. Only when seeing it implemented and applied to an actual problem a developer may face does it actually "click" and become relevant.
@@roydonk2878 very true, though, that's the problem with most tutorials about any abstract subject.
Oddly enough I originally went to college to be a researcher in physics and that sort of issue happens constantly when learning math. "This is what this equations does. Memorize it. Look, *writes out equation and solves it in minutes* its so easy."
I really appreciate videos like this and the people who make them because it has become apparent that teaching (like actual teaching) is a skill not everyone can learn. There are lots of "teachers" in the world and yet so few who are actually able to teach. I'm thankful Tim is someone who can actually teach a subject instead of just reading the definition out load.
Its the hardest thing about learning new or advanced areas in coding, is that the simplicity of the example environment, obscures the usefulness of the new tool.
That is where practice helps. Trying out what you are learning can reveal what you missed or what was not taught. Then you know the right questions to ask to go deeper.
Thank you so much for all the hard work you put into making this content. Seriously one of the best, if not THE best C# tutorials I've found so far.
You are welcome.
Understanding the concept is easy but actually thinking "I could use a delegate for that" while coding, this needs a lot of experience. The problem: as long as you don't use it you will forget it. I'm kinda stuck now.
Practice them for a while. That will help them stick. You don't need to create "real" projects to test what you learn. Just simple little test cases.
Sir have you covered Entity Framework in your videos?
COMMANDER he is in his next course coming soon
I cover it only in regards to ASP.Net authentication. Here is why I won't do it more: iamtimcorey.com/ask-tim-dont-use-entity-framework/
- The best explanation of Delegate.
- The best part of this video is that the focus is on details and that is where the devil lies.
- Keep up the good work Tim Corey. :)
Thank you!
This tutorial is better than the one on pluralsight for sure. However, it's still a little confusing having three different types of delegates passed into a single function, especially as a tutorial. I also noticed a few times you mentioned this isn't how we would actually want to do it, which is usually not something you should be showing people who have absolutely no idea what delegates are. I like to learn best practices, and while this isn't a tutorial on best practices, I want to see delegates used in cases where it makes sense to use them, where they are one of the best solutions for a particular problem.
I really would have liked to see some cleanup, instead of using 3 delegates, clean it up and just use 1.
He still encompassed the power of delegates and their use if you watch to the end. He mentioned "this isn't how you'd be using delegates" as a preface to saying he was over using them to show the different types. Stop relying on him and use your programmer mind. How would you condense it into 1? Its easy, all those delegates can actually be made into one single function and delegate. You can do the whole calculation, and message alerts, using one method, and pass that single method to a delegate that returns what you need. He just extrapolated it into the different types for educative purposes.
It doesn't mean it isn't the proper way to use delegates. This is still the proper way. If you watched the WinUI section of the video, you will see how convenient those delegates ended up being. You can run code in classes completely unrelated and have it compile and work.
Most of the videos does not explain the concept, and they just start coding.
Delegates provide ability to pass methods as parameters to other methods. So that other methods can execute them. In Javascript functions are objects. So passing a function as parameter to other methods is not a problem. But in C#, you must add the function reference to a delegate object, and then it can be passed to another method, which can execute it as and when needed. Most popular use of delegates is in implementing callback methods or event handlers. C# EVENTS use delegate internally to implement events and event handlers.
The PUBLISHER class declares a delegate, and then an event which uses the delegate internally. Then raises the event as and when needed.
The SUBSCRIBER class subscribes to the event of publisher. Internally, it just adds the EventHandler method reference to the delegate of SUBSCRIBER. That is the whole story.
I’m confused. Are you saying my video did not explain that or that other videos do not explain that but I did?
@@IAmTimCorey idk what this commenter's point is either. Most videos over explain mostly on why you should use certain concepts but they fail to show actual coding examples. I like that about your videos. I don't fully understand concepts until I see their application. I appreciate your videos. Also caught you on .NET Rocks
Delegates seem like a strongly-typed version of JavaScript callback functions. Would that be a fair comparison?
That's fair: stackoverflow.com/questions/290819/are-delegates-and-callbacks-the-same-or-similar
@@IAmTimCorey or C++ pointers, right?
I love the way you explain things. Delegates have been a closed book for me until now. Now I get it.
Excellent!
thank you I am from viet nam
You are welcome.
Thank you! Great tutorial. Clear explanations :-)
You are welcome.
Thank you TIm, for these awesome videos. I can learn anything in C# with these videos.
You are welcome.
Hi Tim, thanks for this video, I would like to ask you about what is the video where you talk how to use delegates in a async way?
Thanks! You are the best 🌹
Thank you!
believe me i am a beginner , and this video is so confusing
This isn't a beginner video. It is a video for learning delegates for the first time but delegates are an advanced topic. If you want to learn C# in order, check out my Foundation in C# course series at www.iamtimcorey.com/p/complete-foundation-in-c-course-series It will start you from the beginning and take you through to a place where you could be a junior or even mid-level C# developer.
I just realized that there was an editing mistake.
The video has near-duplicate sections at 49:58 and at 50:23. Threw me off there for a second.
The first duplicate already includes the method "PrintOutDiscountAlert".
The second duplicate the "PrintOutDuplicateAlert" is added.
Hi Tim, Excellent video as always! Got a clear picture of delegates. Just one question. When I try to print currency like you did here in video (C2), it's not displaying in the console. Instead, question mark (?) is printing like below. Any suggestions?
Example oonsole output --> The subTotal for items in cart 1 is ? 45.42
Is the culture known in your project? Depening on the culture it could be a $-mark or a €-mark. Maybe when the culture is unknown, ? is displayed?
Anyone coming to this from C++ -- delegates = function pointers.
Thanks for sharing.
My brains is exploiting, I understood but I still don’t know how to apply it in my applications, I mean I can change one method in my application but I can also change them all so what’s the limit
I can give you an example of one place we use Func in our application where I work now. Maybe that will help a little.
We have a "CacheService" which stores values against a key. The service has one method called "GetOrCreateValue" which takes in a string, which is the key, and a Func. Since we use the cache service in many places in the application, the logic of how we create the value is different everywhere, so that logic can't be added to the cache service. All the cache service does is check in the cache for a value with that key, if it finds it, it returns it. If it doesn't find it then it will run whatever the Func is, then store the value for next time.
I can try to explain a little better if this was confusing but I'm hoping a real world example might be useful :)
Your channel is awesome, this helped me so much!! Thank you so much!!
You are welcome.
I think this video was helpful as the title states for a practical demonstration, but not sure if the concepts were explained well enough for someone that is watching that doesn't have a lot of experience using delegates. Although, I do understand that we use Func and Action Delegates all the time without having a sound understanding of what delegates are. Just wondering why you didn't mention anything about Callbacks? Sorry if I was to critical, but I am just trying to get a good understanding of Delegates so I can exploit their full potential. Thanks !!!
A callback is a delegate. It is just another word for it. My recommendation would be to practice what I showed you in the video. That will help give you a firmer grasp on the subject. The problem with delegates/callbacks/actions/events/etc. is that they are a bit complex and there are tons of fancy names being thrown around that makes matters worse instead of better. My remedy is always to get your hands dirty and see what things actually do for yourself. That way, you can have a frame of reference when you are reading confusing terms. I hope that helps. And no, I didn't read that as critical, but thanks for clarifying. I'm glad you are trying to get a good handle on the topic.
@@IAmTimCorey Thanks Mr. Corey for that excellent advice. I got some help from someone that understands Delegates well and they have me up to speed. They said they commonly use them to notify the user that some event has occurred or after a process has completed asynchronously. I am looking for other use cases to apply them as well, actually I want to use them in a scenario where I am using an Interface, I'm thinking the ultimate goal is to exploit both the power of interfaces and delegates together. Thanks !!!