Swap vs RealSwap.cs

using System;
using System.Collections.Generic;
using System.Text;

public class MyClass
{
	public static void Swap<T> (T a , T b){
		T x = a;
		a = b;
		b = x;
	}
	public static void RealSwap<T>(ref T a,ref T b){
		T x = a;
		a = b;
		b = x;
	}
	
	public static void RunSnippet()
	{
		System.Text.StringBuilder a,b;
		
		a= new System.Text.StringBuilder("Hello,");
		b= new System.Text.StringBuilder(" World!");
		Swap<StringBuilder>(a,b); //it doesn't really swapping
		RealSwap<StringBuilder>(ref a,ref b);
		
		Console.WriteLine("{0}{1}",b,a);
	}
}