^= Operator Reference C#

The exclusive-OR assignment operator.

An expression of the form

x ^= y

is evaluated as

x = x ^ y 

except that x is only evaluated once. The ^ operator performs a bitwise exclusive-OR operation on integral operands and logical exclusive-OR on bool operands.
The ^= operator cannot be overloaded directly, but user-defined types can overload the ^ operator (see operator).

class XORAssignment
{
    static void Main()
    {
        int a = 0x0c;
        a ^= 0x06;
        Console.WriteLine("0x{0:x8}", a);
        bool b = true;
        b ^= false;
        Console.WriteLine(b);
    }
}
/*
Output:
0x0000000a
True
*/ 

source:msdn