A decrement operator, in the context of C#, is a unary operator. It returns a value of same type, with predefined value equal to the operand value minus one. The decrement operator is denoted by the symbol '—'.
A decrement operator supports both prefix and postfix notations. In case of prefix notation (denoted by --x, where x is a variable), the value of a variable is used in the expression after decrementing its original value. While using postfix notation (x--), the value of a variable before the decrement operation will be considered in the expression. A decrement operator can be used to change the pointer location by subtracting a value equal to the size (or pointer-type) from the address contained in the pointer variable.
A decrement operator is usually used in loop iteration statements or in any context where there is a need to decrement by one unit. Features of decrement operator include:
The value returned by the decrement operator is stored in a location pointing to the variable.
The value returned by the operator becomes the result of the decrement operation.
Types which have predefined decrement operator implementation are numeric types, such as integer, sbyte, short, int, long, char, float, double, decimal, and enumeration type.
User-defined types can overload the decrement operator to implement necessary semantics.
While applying a decrement operator to the pointer, result depends on implementation. Exceptions are not thrown if the operation overflows the pointer domain.
The precedence of decrement operator allows postfix notation to have a higher precedence than the prefix form.
Note that, while using a decrement operator, the operand must be an expression representing a variable, property access, or indexes. Additionally, If the decrement operator is used with prefix notation for operand, the property or indexer must have a get and set accessor to avoid compilation errors. Furthermore, if a decrement operator is used for a pointer, the pointer can be of any type except void*.
A decrement operator should be used to set a variable and not to a value. Usage of a decrement operator more than once in a single expression can cause unpredictable results mostly because of optimization applied by the compiler. Hence, it is suggested to use a decrement operator after understanding the order of evaluation, while using both postfix and prefix notation along with its precedence in the set of C# operators. Postfix and prefix notations of a decrement operator cannot have separate operator implementation.