%= Operator (C# Reference)
The remainder 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 is predefined for numeric types to compute the remainder after division.
The %= operator cannot be overloaded directly, but user-defined types can overload the % operator (see operator (C# Reference)).
Example
class Test2
{
static void Main()
{
int a = 5;
a %= 3;
Console.WriteLine(a);
}
}
// Output: 2