(1) 两者都是按地址传递的，使用后都将改变原来的数值

(5) ref是有进有出，out是只出不进

        string outString = "This is the original outString";
        Console.WriteLine(outString);
        outMethod(out outString);
        Console.WriteLine(outString);

        string refString = "This is the original ref string";
        Console.WriteLine(refString);
        refMethod(ref refString);
        Console.WriteLine(refString);