Guide to the Language

 Anonymous Methods
C# 2.0 also introduced anonymous methods, which can be assigned 
to delegate objects. An anonymous method is specified by using the 
delegate keyword followed by a method parameter list and body. This can 
simplify the delegate’s instantiation since a separate method will not have 
to be defined in order to instantiate the delegate.
MyDelegate f = delegate(string s)
{
System.Console.WriteLine(s);
};
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147
 Lambda Expressions
C# 3.0 went one step further and introduced lambda expressions. They 
achieve the same goal as anonymous methods, but with a more concise 
syntax. A lambda expression is written as a parameter list followed by the 
lambda operator (=>) and an expression.
delegate int MyDelegate(int i);
static void Main()
{
// Anonymous method
MyDelegate a = delegate(int x) { return x * x; };
// Lambda expression
MyDelegate b = (int x) => x * x;
a(5); // 25
b(5); // 25
}
The lambda must match the signature of the delegate. Typically, the 
compiler can determine the data type of the parameters from the context, 
so they do not need to be specified. The parentheses may also be left out if 
the lambda has only one input parameter.
MyDelegate c = x => x * x;
If no input parameters are needed, an empty set of parentheses must 
be specified.
delegate void MyEmptyDelegate();
// ...
MyEmptyDelegate d = () =>
System.Console.WriteLine("Hello");
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148
A lambda expression that only executes a single statement is called an 
expression lambda. The expression of a lambda can also be enclosed in 
curly brackets to allow it to contain multiple statements. This form is called 
a statement lambda.
MyDelegate e = (int x) => {
int y = x * x;
return y;
};