About delegates and Events

Here I create a simple class
public class myclass
{
//member
public int X = 10;
//method
public int Y()
{
if (zee != null)
return zee();
else
return 10;
}
//delegate
public delegate int Z();
//event
public event Z zee;
}

All I have ia a member,method,delegate and event
watch how we use each of them....

//in your main() add this code


myclass m = new myclass();
// for data you can directly grab
int a = m.X;

This is a direct use .. no explanation

// for methods you need to execute
int b = m.Y();
// for methods you need to execute
int b = m.Y();

//For delegates you need instance of method and then execute it.
myclass.Z z = m.Y; // do you see we used myclass.Z instead of m.Z?!!
int c = z();

Let me add couple of code in the class that has main()

// own delegate
public delegate int Z();
// Own method
public int y100()
{
MessageBox.Show("100");
return 100;
}
//Own method
public int y200()
{
MessageBox.Show("200");
return 200;
}

Now I add following code in main()
after earlier code

..........

//For your own delegate freely instantiate -- same as above and execute it.
Z z1 = m.Y;
int d = z1();
// This returns 10-10-10-10
MessageBox.Show(a.ToString() + "-" +
b.ToString() + "-" +
c.ToString() + "-" +
d.ToString());

m.zee += this.y100;
c = z();
// This returns 10-10-100-10
MessageBox.Show(a.ToString() + "-" +
b.ToString() + "-" +
c.ToString() + "-" +
d.ToString());

m.zee += this.y200;
c = z();
// This returns 10-10-200-10
MessageBox.Show(a.ToString() + "-" +
b.ToString() + "-" +
c.ToString() + "-" +
d.ToString());

m.zee -= this.y200;
c = z();
// This returns 10-10-100-10
MessageBox.Show(a.ToString() + "-" +
b.ToString() + "-" +
c.ToString() + "-" +
d.ToString());

// This doesn't return error (even if this.y200 is not part of the event)
m.zee -= this.y200;
c = z();
// This returns 10-10-100-10
MessageBox.Show(a.ToString() + "-" +
b.ToString() + "-" +
c.ToString() + "-" +
d.ToString());

Basically Event creates a place for an arraylist of pointers to execute.

Each pointer is a type of the specified delegate.
That is why
//delegate
public delegate int Z();

//event
public event Z zee;


and our fundamental method has calls
public int Y()
{
if (zee != null)
return zee();
else
return 10;
}


If you read design patterns -- and see OBSERVER patterns -- that is EVENT!!

Delegate makes it simpler to use functio pointers. so that functions can be instantiated and executed.