What's the meaning of "=>" in C#? [duplicate]

Question

Possible Duplicate:
C# Lambda ( => )

For instance

Messenger.Default.Register<AboutToCloseMessage>(this, (msg) =>
        {
            if (msg.TheContainer == this.MyContainer) // only care if my container.
            {
                // decide whether or not we should cancel the Close
                if (!(this.MyContainer.CanIClose))
                {
                    msg.Execute(true); // indicate Cancel status via msg callback.
                }
            }
        });

Answer 1

The

=>

Operator is used for Lambda Expressions.

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

It allows you to define an anonymous function "on the fly" and can be used to create delegates or expression tree types.

Answer 2

It is a lambda, it allows you to create a function easily.

in your example you can also write:

Messenger.Default.Register<AboutToCloseMessage>(this, delegate(Message msg)
{
    if (msg.TheContainer == this.MyContainer) // only care if my container.
    {
        // decide whether or not we should cancel the Close
        if (!(this.MyContainer.CanIClose))
        {
            msg.Execute(true); // indicate Cancel status via msg callback.
        }
    }
});

or even

Messenger.Default.Register<AboutToCloseMessage>(this, foobar);

// somewhere after //
private void foobar(Message msg)
{
    if (msg.TheContainer == this.MyContainer) // only care if my container.
    {
        // decide whether or not we should cancel the Close
        if (!(this.MyContainer.CanIClose))
        {
            msg.Execute(true); // indicate Cancel status via msg callback.
        }
    }
}