C# 0 The Complete Reference

Bitwise Compound Assignments

All of the binary bitwise operators can be used in compound assignments. For example, the 

following two statements both assign to 

x

 the outcome of an XOR of 

x

 with the value 127:

x = x ^ 127;

x ^= 127;

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The ? Operator

One of C#’s most fascinating operators is the 

?

, which is C#’s conditional operator. The 

?

operator is often used to replace certain types of if-then-else constructions. The 

?

 is called 

a

ternary operator

 because it requires three operands. It takes the general form

Exp1

 ? 

Exp2

 : 

Exp3

;

where 

Exp1

is a 

bool

 expression, and 

Exp2

 and 

Exp3

 are expressions. The type of 

Exp2

 and 

Exp3

 must be the same. Notice the use and placement of the colon.

The value of a 

?

 expression is determined like this: 

Exp1

 is evaluated. If it is true, then 

Exp2

 is evaluated and becomes the value of the entire 

?

 expression. If 

Exp1

 is false, then 

Exp3

 is evaluated, and its value becomes the value of the expression. Consider this example, 

which assigns 

absval

 the absolute value of 

val

:

absval = val < 0 ? -val : val; // get absolute value of val

Here, 

absval

 will be assigned the value of 

val

 if 

val

 is zero or greater. If 

val

 is negative, then 

absval

 will be assigned the negative of that value (which yields a positive value).

Here is another example of the 

?

 operator. This program divides two numbers, but will 

not allow a division by zero.

// Prevent a division by zero using the ?.

using System;

class NoZeroDiv {

  static void Main() {

    int result;

    for(int i = -5; i < 6; i++) {

      result = i != 0 ? 100 / i : 0;

      if(i != 0)

        Console.WriteLine("100 / " + i + " is " + result);

    }

  }

}

The output from the program is shown here:

100 / -5 is -20

100 / -4 is -25

100 / -3 is -33

100 / -2 is -50

100 / -1 is -100

100 / 1 is 100

100 / 2 is 50

100 / 3 is 33

100 / 4 is 25

100 / 5 is 20

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