C# 4.0 Pocket Reference, 3rd Edition

Expressions and Operators

An expression essentially denotes a value. The simplest kinds of expressions are constants (such as 123) and variables (such as x). Expressions can be transformed and combined using operators. An operator takes one or more input operands to output a new expression:

12 * 30   // * is an operator; 12 and 30 are operands.

Complex expressions can be built because an operand may itself be an expression, such as the operand (12 * 30) in the following example:

1 + (12 * 30)

Operators in C# are classed as unary, binary, or ternary—depending on the number of operands they work on (one, two, or three). The binary operators always use infix notation, where the operator is placed between the two operands.

Operators that are intrinsic to the basic plumbing of the language are called primary; an example is the method call operator. An expression that has no value is called a void expression:

Console.WriteLine (1)

Since a void expression has no value, it cannot be used as an operand to build more complex expressions:

1 + Console.WriteLine (1)      // Compile-time error

Assignment Expressions

An assignment expression uses the = operator to assign the result of another expression to a variable. For example:

x = x * 5

An assignment expression is not a void expression. It actually carries the assignment value, and so can be incorporated into another expression. In the following example, the expression assigns 2 to x and 10 to y:

y = 5 * (x = 2)

This style of expression can be used to initialize ...