-= 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).
Example
// cs_operator_subtraction_assignment.cs
using System;
class MainClass
{
static void Main()
{
int a = 5;
a -= 6;
Console.WriteLine(a);
}
}
Output
-1