C# 0 The Complete Reference

PART I

C h a p t e r   2 0 :  

U n s a f e   C o d e ,   P o i n t e r s ,   N u l l a b l e   T y p e s ,   a n d   M i s c e l l a n e o u s   T o p i c s  

605

PART IPART I

  // Implement a partial method.

  partial void Show() {

    Console.WriteLine("{0}, {1}", X, Y);

  }

}

partial class XY {

  public int Y { get; set; }

  // Call a partial method.

  public void ShowXY() {

    Show();

  }

}

class Test {

  static void Main() {

    XY xy = new XY(1, 2);

    xy.ShowXY();

  }

}

Notice that 

Show( )

 is declared in one part of 

XY

 and implemented by another part. 

The implementation displays the values of 

X

 and 

Y

. This means that when 

Show( )

 is called 

by

ShowXY( )

, the call has effect, and it will, indeed, display 

X

 and 

Y

. However, if you 

comment-out the implementation of 

Show( )

, then the call to 

Show( )

 within 

ShowXY( )

does nothing.

Partial methods have several restrictions, including these: They must return 

void

. They 

cannot have access modifiers. They cannot be virtual. They cannot use