Lambda expressions and expression trees

1. introducing the Func<…> delegate types

  Here are the signatures
of all the Func delegate types:
public delegate TResult Func<TResult>()
public delegate TResult Func<T,TResult>(T arg)
public delegate TResult Func<T1,T2,TResult>(T1 arg1, T2 arg2)
public delegate TResult Func<T1,T2,T3,TResult>
(T1 arg1, T2 arg2, T3 arg3)
public delegate TResult Func<T1,T2,T3,T4,TResult>
(T1 arg1, T2 arg2, T3 arg3, T4 arg4)

Func<string,double,int> is equivalent to a delegate type of the form
delegate int SomeDelegate(string arg1, double arg2)

 

Func<string> returnHello;
            Func<string, string> returnContent;
            Func<string, int> returnLength;

            returnHello = () => { return "Hi David!"; };
            returnContent = (string text) => { return text; };
            returnLength = (string text) => { return text.Length; };

            Console.WriteLine(returnHello());
            Console.WriteLine(returnContent("Hi David!"));
            Console.WriteLine("Length of content: " + returnLength("Hi David!"));