public delegate void MyDelegate(string mydelegate);//声明一个delegate对象

//实现有相同参数和返回值的函数
        public void HelloDelegate(string mydelegate)
        {
            Console.WriteLine(mydelegate);
        }

MyDelegate mydelegate = new MyDelegate(testClass.HelloDelegate);//产生delegate对象
mydelegate("Hello delegate");//调用

From MSDN: [C# delegate的演进]

class Test

{

    delegate void TestDelegate(string s);

    static void M(string s)

    {

        Console.WriteLine(s);

    }

    static void Main(string[] args)

    {

        // Original delegate syntax required

        // initialization with a named method.

        TestDelegate testDelA = new TestDelegate(M);

        // C# 2.0: A delegate can be initialized with

        // inline code, called an "anonymous method.匿名函式" This

        // method takes a string as an input parameter.

        TestDelegate testDelB = delegate(string s) { Console.WriteLine(s); };

        // C# 3.0. A delegate can be initialized with

        // a lambda expression. The lambda also takes a string

        // as an input parameter (x). The type of x is inferred by the compiler.

        TestDelegate testDelC = (x) => { Console.WriteLine(x); };

        // Invoke the delegates.

        testDelA("Hello. My name is M and I write lines.");

        testDelB("That's nothing. I'm anonymous and ");

        testDelC("I'm a famous author.");

        // Keep console window open in debug mode.

        Console.WriteLine("Press any key to exit.");

        Console.ReadKey();

    }

}

/* Output:

    Hello. My name is M and I write lines.

    That's nothing. I'm anonymous and

    I'm a famous author.

    Press any key to exit.

 */

=====Declaring an event=====   
1, To declare an event inside a class, first a delegate type for the event must be declared, if none is already declared.

public delegate void ChangedEventHandler(object sender, EventArgs e);

2, Next, the event itself is declared.

public event ChangedEventHandler Changed;

3, Invoking an event

if (Changed != null)

Changed(this, e);
4, Hooking up to an event

• Compose a new delegate onto that field.

// Add "ListChanged" to the Changed event on "List":

List.Changed += new ChangedEventHandler(ListChanged);

• Remove a delegate from a (possibly composite) field.

// Detach the event and delete the list:

List.Changed -= new ChangedEventHandler(ListChanged);