C#•14mo ago

First time using delegates/lambda expressions

Hi, I've watched countless videos on delegates and lambda expressions but I can't really seem to get my head around them. I'm currently playing around with them and I'm wondering why is this second testDelegate not throwing an error without defining it's type as a delegate? The only difference is that the second one uses a lambda expression to assign it. If someone could give me a little explanation on why this is, that'd be great. I sort of understand how delegates work - they point to a function and this can be changed/added to, so that it runs a different function or more than 1 function each time it is called. Lambda expressions just confuse me however, all I've got from these videos is that it is referred to as a "go to" expression and can be used in LINQ functions like .Where and .OrderBy to sort lists and such

20 Replies

this_is_pain•14mo ago

the lambda type is compatible with the delegate, it's just Action, so why should there be an issue?

nOP•14mo ago

No i'm not saying there's an issue, I'm wondering why what I wrote works why it's correct and why i don't have to use the type delegate

this_is_pain•14mo ago

because types can be automatically deduced

nOP•14mo ago

is that only with lambda? because when i remove the delegate type from the first statement it throws an error

this_is_pain•14mo ago

what do you mean, remove how (also you can paste the $code here) not working 😐 $code

MODiX•14mo ago

To post C# code type the following: ```cs // code here ``` Get an example by typing $codegif in chat For longer snippets, use: https://paste.mod.gg/

nOP•14mo ago

so this is correct

// anonymous method
TestDelegate testDelegate = delegate () { Console.WriteLine("Hello!"); };

// anonymous method with lambda expression
testDelegate += () => { Console.WriteLine("Hello 2!"); };

// anonymous method
TestDelegate testDelegate = delegate () { Console.WriteLine("Hello!"); };

// anonymous method with lambda expression
testDelegate += () => { Console.WriteLine("Hello 2!"); };

but when i remove delegate from the top line

// anonymous method
TestDelegate testDelegate = () { Console.WriteLine("Hello!"); };

// anonymous method with lambda expression
testDelegate += () => { Console.WriteLine("Hello 2!"); };

// anonymous method
TestDelegate testDelegate = () { Console.WriteLine("Hello!"); };

// anonymous method with lambda expression
testDelegate += () => { Console.WriteLine("Hello 2!"); };

it doesnt like that, but the line with the lambda expression doesnt have it

Vi Ness•14mo ago

If you remove the => it doesn't like that either. It looks like it's just two different ways of doing the same thing. This is the first time I've seen using the delegate keyword to create an anonymous method instead of a lambda

nOP•14mo ago

I see, I think the video I was watching first did it using the delegate keyword to show what it is doing in more simple terms then

this_is_pain•14mo ago

this TestDelegate testDelegate = () { Console.WriteLine("Hello!"); }; is not correct like it's not valid syntax

nOP•14mo ago

so what exactly is the lamba expression doing in the second line that the first line isnt doing i don't fully understand lambda expressions yet

this_is_pain•14mo ago

the delegate keyword enables a syntax to define inline/anonymous methods or declare a signature the lambda => is a syntax to declare an inline method if you look at the resulting type, probably both of them ends in an Action so these two

var method1 = delegate () { };
var method2 = () => { };

var method1 = delegate () { };
var method2 = () => { };

var is Action in both cases other features, like static, are present in both cases i believe context is captured in the same way too but i should check honestly and if you look at the definition of Action, it is defined as a delegate

nOP•14mo ago

I kind of see what you're saying i might need to jump back to something simpler if i want to understand this though because i still can't really get my head around it thank you for your help though

this_is_pain•14mo ago

also i believe this testDelegate += () => { Console.WriteLine("Hello 2!"); }; technically is a MulticastDelegate now and also there is the complication of the MethodGroup, because you can have method that is overloaded just as a reference in case you return to this anyway as long as a lambda is compatible with a delegate you will receive no warnings when you pass to one or the other although it seems that your difficulty is more with the syntax than the meaning

nOP•14mo ago

I think it's a bit of both, and more of like when to actually use the lambda expression, I think it'll come with more practice though and yeah that was a multicast delegate, I never thought about it using overloaded methods though that's interesting

this_is_pain•14mo ago

lambda syntax is more modern, essentially that's the one to use do have a less clunky code

Thinker•14mo ago

Literally no one uses the delegate () {} syntax anymore, it's incredibly old

Roan•14mo ago

public event EventHandler NewEvent; <--- this automatically creates a delegate for you to! public event EventHandler<CustomEventArgs> NewEvent; <--- For when you need custom args.

blinkbat•14mo ago

TestDelegate testDelegate = () { Console.WriteLine("Hello!"); }; this isn't valid btw

this_is_pain•14mo ago

how would the compiler know how to interpret that you need something more

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