The Assignment Operator

The assignment operator is the single equal sign, =. The assignment operator works in C# much as it does in any other computer language. It has this general form:

 var = expression; 

Here, the type of var must be compatible with the type of expression.

The assignment operator does have one interesting attribute that you may not be familiar with: It allows you to create a chain of assignments. For example, consider this fragment:

 int x, y, z; x = y = z = 100; // set x, y, and z to 100

This fragment sets the variables x, y, and z to 100 using a single statement. This works because the = is an operator that yields the value of the right-hand expression. Thus, the value of z = 100 is 100, which is then assigned to y, which in turn is assigned to x. Using a "chain of assignment" is an easy way to set a group of variables to a common value.

Compound Assignments

C# provides special compound assignment operators that simplify the coding of certain assignment statements. Let's begin with an example. The assignment statement shown here:

 x = x + 10;

can be written using a compound assignment as

 x += 10;

The operator pair += tells the compiler to assign to x the value of x plus 10.

Here is another example. The statement

 x = x - 100;

is the same as

 x -= 100;

Both statements assign to x the value of x minus 100.

There are compound assignment operators for all the binary operators (that is, those that require two operands). The general form of the shorthand is

 var op = expression; 

Thus, the arithmetic and logical assignment operators are

+=	−=	*=	/=
%=	&=	|=	^=

Because the compound assignment statements are shorter than their noncompound equivalents, the compound assignment operators are also sometimes called the shorthand assignment operators.

The compound assignment operators provide two benefits. First, they are more compact than their “longhand” equivalents. Second, they can result in more efficient executable code (because the operand is evaluated only once). For these reasons, you will often see the compound assignment operators used in professionally written C# programs.