On an afterthought

>>And if you use 'ref' you are forced to instantiate the objects before the call otherwise it won't compile ; 'out' avoids that....

Nowhere is it written that you have to instantiate the objects before the call - only that they have to be initialized

A null value is ok

	static class Test_RefOut
	{
		internal static void Go()
		{
			Dictionary<string, string> dict = null;

			int x = GetDictByRef(ref dict);

			Console.WriteLine("result : {0}", dict);
		}

		static int  GetDictByRef(ref Dictionary<string, string> dict)
		{
			//dict = new Dictionary<string, string>();
			return 2;
		}
		
	}