C# – What Does () => Mean?

c#-3.0

I've been reading through the source code for Moq and I came across the following unit test:

Assert.Throws<ArgumentOutOfRangeException>(() => Times.AtLeast(0));

And for the life of me, I can't remember what () => actually does. I'm think it has something to do with anonymous methods or lambdas. And I'm sure I know what it does, I just can't remember at the moment….

And to make matters worse….google isn't being much help and neither is stackoverflow

Can someone give me a quick answer to a pretty noobish question?

Best Answer

Search StackOverflow for "lambda".

Specifically:

() => Console.WriteLine("Hi!");

That means "a method that takes no arguments and returns void, and when you call it, it writes the message to the console."

You can store it in an Action variable:

Action a = () => Console.WriteLine("Hi!");

And then you can call it:

a();

Related Solutions

C# – What Does the ‘=>’ Syntax Mean?

It's the lambda operator.

From C# 3 to C# 5, this was only used for lambda expressions. These are basically a shorter form of the anonymous methods introduced in C# 2, but can also be converted into expression trees.

As an example:

Func<Person, string> nameProjection = p => p.Name;

is equivalent to:

Func<Person, string> nameProjection = delegate (Person p) { return p.Name; };

In both cases you're creating a delegate with a Person parameter, returning that person's name (as a string).

In C# 6 the same syntax is used for expression-bodied members, e.g.

// Expression-bodied property
public int IsValid => name != null && id != -1;

// Expression-bodied method
public int GetHashCode() => id.GetHashCode();

C# Syntax – What Does ‘() =>’ Mean?

It's a lambda expression that takes 0 arguments

http://msdn.microsoft.com/en-us/library/bb397687.aspx

Best Answer

Related Solutions

C# – What Does the ‘=>’ Syntax Mean?

C# Syntax – What Does ‘() =>’ Mean?

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