反射与特性

示例代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace MyAttribute.Extension
{
    /// <summary>
    /// 用户状态
    /// </summary>
    public enum UserState
    {
        /// <summary>
        /// 正常
        /// </summary>
        [Remark("正常")]
        Normal = 0,//左边是字段名称  右边是数据库值   哪里放描述？  注释
        /// <summary>
        /// 冻结
        /// </summary>
        [Remark("冻结")]
        Frozen = 1,
        /// <summary>
        /// 删除
        /// </summary>
        //[Remark("删除")]
        Deleted = 2
    }
    //枚举项加一个描述   实体类的属性也可以Display  
    //别名   映射  
    public class RemarkAttribute : Attribute
    {
        public RemarkAttribute(string remark)
        {
            this._Remark = remark;
        }
        private string _Remark = null;
        public string GetRemark()
        {
            return this._Remark;
        }
    }


    public static class RemarkExtension
    {
        public static string GetRemark(this Enum value)
        {
            Type type = value.GetType();
            FieldInfo field = type.GetField(value.ToString());
            if (field.IsDefined(typeof(RemarkAttribute), true))
            {
                RemarkAttribute attribute = (RemarkAttribute)field.GetCustomAttribute(typeof(RemarkAttribute), true);
                return attribute.GetRemark();
            }
            else
            {
                return value.ToString();
            }
        }

    }
}

using MyAttribute.Extension;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MyAttribute
{
    /// <summary>
    /// 这里是注释，除了让人看懂这里写的是什么，
    /// 对运行没有任何影响
    /// </summary>
    //[Obsolete("请不要使用这个了，请使用什么来代替", true)]//影响编译器的运行
    //[Serializable]//可以序列化和反序列化  可以影响程序的运行
    //MVC filter   ORM table  key  display   wcf 

    //[Custom]
    //[Custom()]
    //[Custom(123), Custom(123, Description = "1234")]
    [Custom(123, Description = "1234", Remark = "2345")]//方法不行
    public class Student
    {
        [CustomAttribute]
        public int Id { get; set; }
        [Leng(5,10)]//还有各种检查
        public string Name { get; set; }
        [Leng(20, 50)]
        public string Accont { get; set; }

        /// <summary>
        /// 10001~999999999999
        /// </summary>
        [Long(10001, 999999999999)]
        public long QQ { get; set; }


        //private long _QQ2 = 0;//解决数据合法性，给属性增加了太多的事儿
        //public long QQ2
        //{
        //    get
        //    {
        //        return this._QQ2;
        //    }
        //    set
        //    {
        //        if (value > 10001 && value < 999999999999)
        //        {
        //            _QQ2 = value;
        //        }
        //        else
        //        {
        //            throw new Exception();
        //        }
        //    }
        //}
        [CustomAttribute]
        public void Study()
        {
            Console.WriteLine($"这里是{this.Name}");
        }

        [Custom()]
        [return: Custom()]
        public string Answer([Custom]string name)
        {
            return $"This is {name}";
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace MyAttribute.Extension
{
    public static class ValidateExtension
    {
        public static bool Validate(this object oObject)
        {
            Type type = oObject.GetType();
            foreach (var prop in type.GetProperties())
            {
                if (prop.IsDefined(typeof(AbstractValidateAttribute), true))
                {
                    object[] attributeArray = prop.GetCustomAttributes(typeof(AbstractValidateAttribute), true);
                    foreach (AbstractValidateAttribute attribute in attributeArray)
                    {
                        if (!attribute.Validate(prop.GetValue(oObject)))
                        {
                            return false;//表示终止
                        }
                    }
                }

                //if (prop.IsDefined(typeof(LongAttribute), true))
                //{
                //    LongAttribute attribute = (LongAttribute)prop.GetCustomAttribute(typeof(LongAttribute), true);
                //    if (!attribute.Validate(prop.GetValue(oObject)))
                //    {
                //        return false;
                //    }
                //}
                //if (prop.IsDefined(typeof(LengAttribute), true))
                //{
                //    LengAttribute attribute = (LengAttribute)prop.GetCustomAttribute(typeof(LengAttribute), true);
                //    if (!attribute.Validate(prop.GetValue(oObject)))
                //    {
                //        return false;
                //    }
                //}
            }
            return true;
        }
    }

    public abstract class AbstractValidateAttribute : Attribute
    {
        public abstract bool Validate(object value);
    }

    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field)]
    public class LengAttribute : AbstractValidateAttribute
    {
        private int _Min = 0;
        private int _Max = 0;
        public LengAttribute(int min, int max)
        {
            this._Min = min;
            this._Max = max;
        }


        public override bool Validate(object value)//" "
        {
            if (value != null && !string.IsNullOrWhiteSpace(value.ToString()))
            {
                int length = value.ToString().Length;
                if (length > this._Min && length < this._Max)
                {
                    return true;
                }
            }
            return false;
        }
    }
    public class LongAttribute : AbstractValidateAttribute
    {
        private long _Min = 0;
        private long _Max = 0;
        public LongAttribute(long min, long max)
        {
            this._Min = min;
            this._Max = max;
        }


        public override bool Validate(object value)//" "
        {
            //可以改成一句话
            if (value != null && !string.IsNullOrWhiteSpace(value.ToString()))
            {
                if (long.TryParse(value.ToString(), out long lResult))
                {
                    if (lResult > this._Min && lResult < this._Max)
                    {
                        return true;
                    }
                }
            }
            return false;
        }
    }
}