public static T DeepCopy<T>(T obj)
        {
            //如果是字符串或值类型则直接返回
            if (obj==null||obj is string || obj.GetType().IsValueType) return obj;

            object retval = Activator.CreateInstance(obj.GetType());
            System.Reflection.FieldInfo[] fields = obj.GetType().GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static);
            foreach (System.Reflection.FieldInfo field in fields)
            {
                try { field.SetValue(retval, DeepCopy(field.GetValue(obj))); }
                catch { }
            }
            return (T)retval;
        }