Using signs + and - for swapping of two values.

using system;

namespace TestConsole
{
class Program
{
static void Main()
{
int a = 10;
int b = 20;
Console.write("After swap a = {0} and b = {1}", a, b);
a = a + b; // a * b
b = a - b; // a / b
a = a - b; // a / b
Console.Write("After swap a = {0} and b = {1}", a, b);
}
}
}