C# 随机给一个全部信息都未知的类类型,如何获取该类的类名、属性个数、属性名、属性的数据类型、属性值?

语言: CN / TW / HK

一、场景假设

假设现在有一个泛型类T的实例对象t,该T类的全部信息都未知。

要求:打印输出实例对象t的类名、属性个数、属性名、属性的数据类型、属性值。

二、解决问题

1、我们根据输出的内容要求定义一个实体类如下:

public class GeneralDataModel
    {
        /// <summary>
        /// 类名
        /// </summary>
        public string class_name { get; set; }

        /// <summary>
        /// 属性个数
        /// </summary>
        public int prop_count { get; set; }

        /// <summary>
        /// 单个属性的信息
        /// </summary>
        public List<PropInfoItem> props { get; set; }
    }
    public class PropInfoItem
    {
        /// <summary>
        /// 属性名
        /// </summary>
        public string prop_name { get; set; }

        /// <summary>
        /// 属性数据类型
        /// </summary>
        public string prop_data_type { get; set; }

        /// <summary>
        /// 属性值
        /// </summary>
        public string prop_value { get; set; }
    }

2、编写一个方法,该方法的主要功能是解析实例对象t,并输出步骤1中格式的内容。方法代码实现如下:

public static GeneralDataModel DataAnalysis<T>(T t)
        {
            var data_type = t.GetType();
            var propInfo = data_type.GetProperties();
            var list = new List<PropInfoItem>();
            foreach (var item in propInfo)
            {
                var e = new PropInfoItem
                {
                    prop_name = item.Name,
                    prop_data_type = item.PropertyType.Name,
                    prop_value = item.GetValue(t) == null ? "" : item.GetValue(t).ToString()
                };
                list.Add(e);
            }

            var res = new GeneralDataModel
            {
                class_name = data_type.Name,
                prop_count = propInfo.Count(),
                props = list
            };

            return res;
        }

三、验证方法功能

1、假设现在有一个学生类如下所示:

public class Student
    {
        /// <summary>
        /// 学号
        /// </summary>
        public int no { get; set; }

        /// <summary>
        /// 姓名
        /// </summary>
        public string name { get; set; }

        /// <summary>
        /// 年级
        /// </summary>
        public string grade { get; set; }

        /// <summary>
        /// 出生年月
        /// </summary>
        public DateTime birth { get; set; }
    }

2、根据该类实例化了一个st对象如下:

var st = new Student()
   {
       no = 123456,
       name = "张三",
       grade = "六年级",
       birth = DateTime.Now
    };

3、调用DataAnalysis方法解析st,并打印输出结果:

var res = DataAnalysis(st); 
   Console.WriteLine(JsonConvert.SerializeObject(res));

4、输出结果如下:

{
    "class_name": "Student",
    "prop_count": 4,
    "props": [
        {
            "prop_name": "no",
            "prop_data_type": "Int32",
            "prop_value": "123456"
        },
        {
            "prop_name": "name",
            "prop_data_type": "String",
            "prop_value": "张三"
        },
        {
            "prop_name": "grade",
            "prop_data_type": "String",
            "prop_value": "六年级"
        },
        {
            "prop_name": "birth",
            "prop_data_type": "DateTime",
            "prop_value": "2022/5/7 17:21:12"
        }
    ]
}

5、看到输出结果后,感觉完美的解决了问题。

四、变化无常

1、因为种种原因,学生类增加了两个属性,同时实例化对象的创建形式也变了,变化后的形式如下:

public class Student
    {
        public Student()
        {

        }

        public Student(string id_card_no, string address)
        {
            this.id_card_no = id_card_no;
            this.address = address;
        }


        /// <summary>
        /// 学号
        /// </summary>
        public int no { get; set; }

        /// <summary>
        /// 姓名
        /// </summary>
        public string name { get; set; }

        /// <summary>
        /// 年级
        /// </summary>
        public string grade { get; set; }

        /// <summary>
        /// 出生年月
        /// </summary>
        public DateTime birth { get; set; }

        /// <summary>
        /// 身份证(受保护类型)
        /// </summary>
        protected string id_card_no { get; set; }

        /// <summary>
        /// 家庭地址(私有类型)
        /// </summary>
        private string address { get; set; }
    }
var st = new Student("777888202005071111", "家庭地址私有,暂时不方便透露")
   {
       no = 123456,
       name = "张三",
       grade = "六年级",
       birth = DateTime.Now
   };

2、再次调用DataAnalysis方法解析st,并打印输出结果:

var res = DataAnalysis(st);
   Console.WriteLine(JsonConvert.SerializeObject(res));

3、输出结果如下:

{
    "class_name": "Student",
    "prop_count": 4,
    "props": [
        {
            "prop_name": "no",
            "prop_data_type": "Int32",
            "prop_value": "123456"
        },
        {
            "prop_name": "name",
            "prop_data_type": "String",
            "prop_value": "张三"
        },
        {
            "prop_name": "grade",
            "prop_data_type": "String",
            "prop_value": "六年级"
        },
        {
            "prop_name": "birth",
            "prop_data_type": "DateTime",
            "prop_value": "2022/5/7 17:40:21"
        }
    ]
}

4、看到输出结果时,咦?怎么似乎好像哪里不对?新增的两个属性怎么没有被解析并输出呢?

五、反射了解一下?

1、通过种种途径或者查阅其他资料你了解到了反射的相关知识,并找到了一个名为GetRuntimeProperties的方法。

2、修改原先的解析方法代码如下:

public static GeneralDataModel DataAnalysis<T>(T t)
    {
        var data_type = t.GetType();
        var refPropInfo = data_type.GetRuntimeProperties();
        var list = new List<PropInfoItem>();
        foreach (var item in refPropInfo)
        {
            var e = new PropInfoItem
            {
                prop_name = item.Name,
                prop_data_type = item.PropertyType.Name,
                prop_value = item.GetValue(t) == null ? "" : item.GetValue(t).ToString()
            };
            list.Add(e);
        }

        var res = new GeneralDataModel
        {
            class_name = data_type.Name,
            prop_count = refPropInfo.Count(),
            props = list
        };

        return res;
    }

3、再一次调用DataAnalysis方法解析st,并打印输出结果:

var res = DataAnalysis(st);
   Console.WriteLine(JsonConvert.SerializeObject(res));

4、输出结果如下:

{
    "class_name": "Student",
    "prop_count": 6,
    "props": [
        {
            "prop_name": "no",
            "prop_data_type": "Int32",
            "prop_value": "123456"
        },
        {
            "prop_name": "name",
            "prop_data_type": "String",
            "prop_value": "张三"
        },
        {
            "prop_name": "grade",
            "prop_data_type": "String",
            "prop_value": "六年级"
        },
        {
            "prop_name": "birth",
            "prop_data_type": "DateTime",
            "prop_value": "2022/5/7 17:52:12"
        },
        {
            "prop_name": "id_card_no",
            "prop_data_type": "String",
            "prop_value": "777888202005071111"
        },
        {
            "prop_name": "address",
            "prop_data_type": "String",
            "prop_value": "家庭地址暂时不方便透露"
        }
    ]
}

5、看到这输出结果,脸上露出了满意的笑容,啊~~~问题终于解决了,开森^_^

六、前后对比并溯源

1、方法前后变化仅仅只有一处,由 GetProperties 变为了 GetRuntimeProperties

2、溯源发现:

  • GetProperties :在System命名空间下,是Type类的实例方法。
  • GetRuntimeProperties (Type类的扩展方法) :在System.Reflection命名空间下,是RuntimeReflectionExtensions类的静态方法。

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