Looking for the name of a C# syntax

Question

I've been away from C# for a while and now that I'm trying to read some code, I'm having a hard time find the meaning of it:

var server = new WebSocketServer("ws://localhost:8181");
server.Start(socket =>
{
    socket.OnOpen = () =>
    {
        Console.WriteLine("Open!");
        allSockets.Add(socket);
    };
    socket.OnClose = () =>
    {
        Console.WriteLine("Close!");
        allSockets.Remove(socket);
    };
    socket.OnMessage = message =>
    {
        Console.WriteLine(message);
        allSockets.ToList().ForEach(s => s.Send("Echo: " + message));
    };
});

What's the name for socket => { .. } syntax and where can I find some text on it? And in which version of C# is it introduced? Is the = () => { .. } the same?

possible duplicate of [C# Lambda expression, why should I use this?](http://stackoverflow.com/questions/167343/c-sharp-lambda-expression-why-should-i-use-this) — nawfal, Jul 03 '14 at 10:28

BlackBear · Answer 1 · 2013-02-09T12:46:57.013

4

It is a lambda expression, basically it is a shortcut for defining delegates, which are anonimous methods. It was introduced in C# 3 along with LINQ to make its use much simpler. Syntax is as follow:

parameters => body

Usually the compiler can infer in some way the type of the parameter, that's why you see only the names of the parameters.

edited Feb 09 '13 at 12:46

answered Feb 09 '13 at 12:39

BlackBear

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Delegates are *references* to methods; they are not actually methods. A delegate can reference a normal method or an anonymous method. A lambda expression is an anonymous method, though. – Matthew Watson Feb 09 '13 at 12:43
@MatthewWatson lambdas are references as well, I just wanted to keep my answer simple – BlackBear Feb 09 '13 at 12:47
Er, not they aren't - they are methods, but you can create a delegate to store a reference to them. http://msdn.microsoft.com/en-gb/library/bb397687.aspx – Matthew Watson Feb 09 '13 at 13:12

score 1 · Accepted Answer · edited May 23 '17 at 11:56

1

in c# this syntax is called Lambda Expressions. They are available since C# 3.0

more about:

Microsoft's Programming Guide explaining lambda expression

C# Lambda expressions: Why should I use them?

and an example of programmersheaven.com

edited May 23 '17 at 11:56

Community

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answered Feb 09 '13 at 12:39

duffy356

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Looking for the name of a C# syntax

2 Answers2