-= Operator (C# Reference)

The subtraction assignment operator.

Remarks

An expression using the -= assignment operator, such as

x -= y  

is equivalent to

x = x - y  

except that x is only evaluated once. The meaning of the - operator is dependent on the types of x and y (subtraction for numeric operands, delegate removal for delegate operands, and so forth).

The -= operator cannot be overloaded directly, but user-defined types can overload the - operator (see operator).

The -= operator is also used in C# to unsubscribe from an event. For more information, see How to: Subscribe to and Unsubscribe from Events.

Example

class MainClass3
{
    static void Main()
    {
        int a = 5;
        a -= 6;
        Console.WriteLine(a);
    }
}
/*
Output:
-1
*/

See Also

C# Reference
C# Programming Guide
C# Operators