What is the difference between lambdas and delegates in the .NET Framework?

Question

I get asked this question a lot and I thought I\'d solicit some input on how to best describe the difference.

Answer 1

One difference is that an anonymous delegate can omit parameters while a lambda must match the exact signature. Given:

public delegate string TestDelegate(int i);

public void Test(TestDelegate d)
{}

you can call it in the following four ways (note that the second line has an anonymous delegate that does not have any parameters):

Test(delegate(int i) { return String.Empty; });
Test(delegate { return String.Empty; });
Test(i => String.Empty);
Test(D);

private string D(int i)
{
    return String.Empty;
}

You cannot pass in a lambda expression that has no parameters or a method that has no parameters. These are not allowed:

Test(() => String.Empty); //Not allowed, lambda must match signature
Test(D2); //Not allowed, method must match signature

private string D2()
{
    return String.Empty;
}