For the sake of future learners, and humanity, I submit this correction to the currently selected answer.
If you want to avoid using temp variables, there are only two sensible options that take first performance and then readability into consideration.
Swap method. (Absolute best performance, next to inline temp variable)Interlocked.Exchange. (5.9 times slower on my machine, but this is your only option if multiple threads will be swapping these variables simultaneously.)Things you should never do:
Decimal is not a CPU primitive and results in far more code than you realize.Because everyone loves hard numbers, here's a program that compares your options. Run it in release mode from outside Visual Studio so that Swap is inlined. Results on my machine (Windows 7 64-bit i5-3470):
Inline: 00:00:00.7351931
Call: 00:00:00.7483503
Interlocked: 00:00:04.4076651
Code:
class Program
{
static void Swap<T>(ref T obj1, ref T obj2)
{
var temp = obj1;
obj1 = obj2;
obj2 = temp;
}
static void Main(string[] args)
{
var a = new object();
var b = new object();
var s = new Stopwatch();
Swap(ref a, ref b); // JIT the swap method outside the stopwatch
s.Restart();
for (var i = 0; i < 500000000; i++)
{
var temp = a;
a = b;
b = temp;
}
s.Stop();
Console.WriteLine("Inline temp: " + s.Elapsed);
s.Restart();
for (var i = 0; i < 500000000; i++)
{
Swap(ref a, ref b);
}
s.Stop();
Console.WriteLine("Call: " + s.Elapsed);
s.Restart();
for (var i = 0; i < 500000000; i++)
{
b = Interlocked.Exchange(ref a, b);
}
s.Stop();
Console.WriteLine("Interlocked: " + s.Elapsed);
Console.ReadKey();
}
}