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  

603

PART IPART I

P

Q

P | Q

P & Q

true

null

true

null

false

null

null

false

null

true

true

null

null

false

null

false

null

null

null

null

One other point: When the 

!

 operator is applied to a 

bool?

 value that is 

null

, the 

outcome is 

null

.

Partial Types

Beginning with C# 2.0, a class, structure, or interface definition can be broken into two or 

more pieces, with each piece residing in a separate file. This is accomplished through the 

use of the 

partial

 keyword. When your program is compiled, the pieces are united.

When used to create a partial type, the 

partial

 modifier has this general form:

partial

type typename

 { // ...

Here, 

typename

 is the name of the class, structure, or interface that is being split into pieces. 

Each part of a partial type must be modified by 

partial

.

Here is an example that divides a simple XY coordinate class into three separate files. 

The first file is shown here:

partial class XY {

  public XY(int a, int b) {

    X = a;

    Y = b;

  }

}

The second file is shown next:

partial class XY {

  public int X { get; set; }

}

The third file is