Lambda expressions

With the C# 3.0 new feature extension method and the C# 2.0 new feature anonymous method (or inline method), Visual Studio introduces a new expression called lambda expression.

Lambda expression is actually a syntax change for anonymous methods. It is just a new way of writing anonymous methods. Next, let's explain what a lambda expression is, step by step.

First, in C# 3.0, there is a new generic delegate type, Func<A,R>, which presents a function taking an argument of type A and returns a value of type R:

delegate R Func<A,R> (A Arg);

In fact there are several overloaded versions of Func of which Func<A,R> is one.

Now we will use this new generic delegate type to define an extension:

public static IEnumerable<T> Get<T>(this IEnumerable<T> source, Func<T, bool> predicate)
{
    foreach (T item in source)
    {
       if (predicate(item))
           yield return item;
    }
}

This extension method will apply to an object that extends...