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7.5.9 Postfix increment and decrement operators

Visual Studio .NET 2003
post-increment-expression:
primary-expression   ++
post-decrement-expression:
primary-expression   --

The operand of a postfix increment or decrement operation must be an expression classified as a variable, a property access, or an indexer access. The result of the operation is a value of the same type as the operand.

If the operand of a postfix increment or decrement operation is a property or indexer access, the property or indexer must have both a get and a set accessor. If this is not the case, a compile-time error occurs.

Unary operator overload resolution (Section 7.2.3) is applied to select a specific operator implementation. Predefined ++ and -- operators exist for the following types: sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, and any enum type. The predefined ++ operators return the value produced by adding 1 to the operand, and the predefined -- operators return the value produced by subtracting 1 from the operand.

The run-time processing of a postfix increment or decrement operation of the form x++ or x-- consists of the following steps:

  • If x is classified as a variable:
    • x is evaluated to produce the variable.
    • The value of x is saved.
    • The selected operator is invoked with the saved value of x as its argument.
    • The value returned by the operator is stored in the location given by the evaluation of x.
    • The saved value of x becomes the result of the operation.
  • If x is classified as a property or indexer access:
    • The instance expression (if x is not static) and the argument list (if x is an indexer access) associated with x are evaluated, and the results are used in the subsequent get and set accessor invocations.
    • The get accessor of x is invoked and the returned value is saved.
    • The selected operator is invoked with the saved value of x as its argument.
    • The set accessor of x is invoked with the value returned by the operator as its value argument.
    • The saved value of x becomes the result of the operation.

The ++ and -- operators also support prefix notation, as described in Section 7.6.5. The result of x++ or x-- is the value of x before the operation, whereas the result of ++x or --x is the value of x after the operation. In either case, x itself has the same value after the operation.

An operator ++ or operator -- implementation can be invoked using either postfix or prefix notation. It is not possible to have separate operator implementations for the two notations.

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