How to understand C# delegates?

See more:

C#

ASP.NET

C#4.0

Consider the example below:

private void button1_Click(object sender, EventArgs e)
   {
     DelegateSample obj = new DelegateSample();
     DelFunc delobj1 = new DelFunc(obj.func1);
     delobj1 += new DelFunc(obj.func2);
     delobj1 += new DelFunc(obj.func3);
     obj.functionAll(delobj1);
   }
 }
 class DelegateSample
 {
   public void func1()
   {
     MessageBox.Show("You just called func1");
   }
   public void func2()
   {
     MessageBox.Show("You just called func2");
   }
   public void func3()
   {
     MessageBox.Show("You just called func3");
   }
   public void functionAll(Delegate o)
   {
   Delegate[] objdel= o.GetInvocationList();
   for (int i = 0; i < objdel.Length; i++)
   {
     DelFunc obj = (DelFunc)objdel[i];
     obj.Invoke();
   }
   }

Here i have a delegate object which references 3 methods.I have added the method references and the delegate object is being passed as an argument to a method.This method is called when the buttom is clicked.Hence I'd like to know how these methods are called during "RUNTIME" when I have already added the references of all the 3 methods in the compile time.