C# Lambda Expressions – What Does ‘=>’ Mean?

.net.net-3.5c++lambda

Forgive me if this screams newbie but what does => mean in C#? I was at a presentation last week and this operator (I think) was used in the context of ORM. I wasn't really paying attention to the specifics of syntax until I went back to my notes.

Best Answer

In C# the lambda operator is written "=>" (usually pronounced "goes to" when read aloud). It means that the arguments on the left are passed into the code block (lambda function / anonymous delegate) on the right.

So if you have a Func or Action (or any of their cousins with more type parameters) then you can assign a lambda expression to them rather than needing to instantiate a delegate or have a separate method for the deferred processing:

//creates a Func that can be called later
Func<int,bool> f = i => i <= 10;
//calls the function with 12 substituted as the parameter
bool ret = f(12);

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# – What Does the Operator ‘=>’ Mean?

Basically it's specifying an anonymous function, that takes no parameters that calls SomeAction. So yes, they are functionally equivalent. Though not equal. Using the lambda is more equivalent to:

del = new SomeDelegate(this.CallSomeAction);

where CallSomeAction is defined as:

public void CallSomeAction()
{
    this.SomeAction();
}

Hope that helps!

Best Answer

Related Solutions

C# – What Does the ‘=>’ Syntax Mean?

C# – What Does the Operator ‘=>’ Mean?

Related Question