■

using System;

namespace Test
{
    class Test
    {
        static void Main()
        {
            string s1, s2;
            s1 = "foo";
            s2 = "bar";
            Console.WriteLine("s1: {0}, s2: {1}", s1, s2);
            Swap(ref s1, ref s2);
            Console.WriteLine("s1: {0}, s2: {1}", s1, s2);
            
            int i1, i2;
            i1 = 0;
            i2 = 1;
            Console.WriteLine("i1: {0}, i2: {1}", i1, i2);
            Swap(ref i1, ref i2);
            Console.WriteLine("i1: {0}, i2: {1}", i1, i2);
        }
        
        static void Swap<T>(ref T lhs, ref T rhs)
        {
            Console.WriteLine("call Swap<{0}>", lhs.GetType());
            T temp = lhs;
            lhs = rhs;
            rhs = temp;
        }
        
        static void Swap(ref int lhs, ref int rhs)
        {
            Console.WriteLine("call Swap");
            int temp = lhs;
            lhs = rhs;
            rhs = temp;
        }
    }
}

> csc try.cs
Microsoft (R) Visual C# 2010 Compiler version 4.0.30319.1
Copyright (C) Microsoft Corporation. All rights reserved.


> try.exe
s1: foo, s2: bar
call Swap<System.String>
s1: bar, s2: foo
i1: 0, i2: 1
call Swap
i1: 1, i2: 0