Compiler Error CS1059

The operand of an increment or decrement operator must be a variable, property or indexer.

This error is raised when you try to increment or decrement a constant value. It can also occur if you try to increment an expression such as (a+b)++.

To correct this error

• Make the variable non-const.

• Remove the increment or decrement operator.

• Store the expression in a variable, and then increment the variable.

Example

The following example generates CS1059 because i is a constant, not a variable, and E is an Enum type, whose elements are also constant values.

// CS1059.cs
    class Program
    {
        public enum E : sbyte
        {
            a = 1,
            b = 2
        }

        static void Main(string[] args)
        {
            const int i = 0;
            i++;            // CS1059
            E test = E.a++; // CS1059
        }
    }

See Also

Reference

Constants (C# Programming Guide)