Lambda expression common syntax-CSharp

There are multiple ways of expressing lambdas, depending on the exact scenario - some examples:

// simplest form; no types, no brackets
Func f1 = x => 2 * x;
// optional exlicit argument brackets
Func f2 = (x) => 2 * x;
// optional type specification when used with brackets
Func f3 = (int x) => 2 * x;
// multiple arguments require brackets (types optional)
Func f4 = (x, y) => x * y;
// multiple argument with explicit types
Func f5 = (int x, int y) => x * y;

The signature of the lambda must match the signature of the delegate used (whether it is explicit, like above, or implied by the context in things like .Select(cust => cust.Name)

You can use lambdas without arguments by using an empty expression list:

// no arguments
Func f0 = () => 12;

Ideally, the expression on the right hand side is exactly that; a single expression. The compiler can convert this to either a delegate or an Expression tree:

// expression tree
Expression> f6 = (x, y) => x * y;

However; you can also use statement blocks, but this is then only usable as a delegate:

// braces for a statement body
Func f7 = (x, y) => {
int z = x * y;
Console.WriteLine(z);
return z;
};

Note that even though the .NET 4.0 Expression trees support statement bodies, the C# 4.0 compiler doesn't do this for you, so you are still limited to simple Expression trees unless you do it "the hard way"; see my article on InfoQ for more information.