The addition 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 (addition for numeric operands, concatenation for string operands, and so forth).
The += operator cannot be overloaded directly, but user-defined types can overload the + operator (see operator).
Example
// cs_operator_addition_assignment.cs
using System;
class MainClass
{
static void Main()
{
int a = 5;
a += 6;
Console.WriteLine(a);
string s = "Micro";
s += "soft";
Console.WriteLine(s);
}
}
Output
11 Microsoft