C# 反射修改私有静态成员变量

//动态链接库中PvsApiIfCtrl.Cls.Cls_Public类有一变量 private static string key="abcd";
//下面通过反射的技术修改和获取值
//设置key 
public static void updatePalmKey(string key = "")
        {
            BindingFlags flag = BindingFlags.Static | BindingFlags.NonPublic;
            FieldInfo f_key = typeof(PvsApiIfCtrl.Cls.Cls_Public).GetField("key", flag);
            f_key.SetValue(new PvsApiIfCtrl.Cls.Cls_Public(), key);
        }

        /// <summary>
        /// 获取key
        /// </summary>
        /// <returns></returns>
        public static string getPalmKey()
        {
            BindingFlags flag = BindingFlags.Static | BindingFlags.NonPublic;
            FieldInfo f_key = typeof(PvsApiIfCtrl.Cls.Cls_Public).GetField("key", flag);
            object o = f_key.GetValue(new PvsApiIfCtrl.Cls.Cls_Public());
            return o.ToString();
        }