|= Operator (C# Reference) 

The OR 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 | operator performs a bitwise logical OR operation on integral operands and logical OR on bool operands.

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

Example

// cs_operator_or_assignment.cs
using System;
class MainClass
{
    static void Main() 
    {
        int a = 0x0c;
        a |= 0x06;
        Console.WriteLine("0x{0:x8}", a);
        bool b = true;
        b |= false;
        Console.WriteLine(b);
    }
}

Output

0x0000000e
True

See Also

Reference

C# Operators

Concepts

C# Programming Guide

Other Resources

C# Reference