利用反射，设置获取自定义特性

1、建立类库及实体类UseInfo.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Entities.Attributes;

namespace Entities
{
    public class UserInfo:BaseModel
    {
        [Column(mapName:"UserName")]
        public string Name { get; set; }
        [Column(minLength: 6, maxLength: 12, errorMess:"no pass",regx:"")]
        public string Pass { get; set; }
        [Format("yyyy-MM-dd")]
        public DateTime AddDateTime { get; set; }
        public bool Enable { get; set; }

        [Format("F2")]
        public decimal Total { get; set; }

        [Column(minLength:0,maxLength:1)]
        public int Status { get; set; }
    }
}

2、建立特性类

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

namespace Entities.Attributes
{

    [AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = true)]
    public class ColumnAttribute:Attribute
    {
        public int? MinLength { get; private set; }

        public int? MaxLength { get; private set; }

        public string ErrorMess { get; private set; }

        public string MapName { get; private set; }

        public string Regx { get; private set; }

        public ColumnAttribute(string mapName, int minLength=0, int maxLength=0, string errorMess=null, string regx=null)
        {
            MinLength = minLength;
            MaxLength = maxLength;
            MapName = mapName;
            ErrorMess = errorMess;
            Regx = regx;
        }

        public ColumnAttribute(string mapName)
        {
            MapName = mapName;
        }

        public ColumnAttribute(string mapName, int minLength = 0)
        {
            MinLength = minLength;
            MapName = mapName;
        }

        public ColumnAttribute(string mapName, int minLength = 0, int maxLength = 0)
        {
            MinLength = minLength;
            MaxLength = maxLength;
            MapName = mapName;
        }

        public ColumnAttribute(string mapName, int minLength = 0, int maxLength = 0, string errorMess = null)
        {
            MinLength = minLength;
            MaxLength = maxLength;
            MapName = mapName;
            ErrorMess = errorMess;
        }

        public ColumnAttribute( int minLength = 0, int maxLength = 0, string errorMess = null, string regx = null)
        {
            MinLength = minLength;
            MaxLength = maxLength;
            ErrorMess = errorMess;
            Regx = regx;
        }
    }

    public static class ColumnEx
    {
        public static string GetName(this PropertyInfo property)
        {
            if (property.IsDefined(typeof(ColumnAttribute), true))
            {
                var attr = Attribute.GetCustomAttribute(property, typeof(ColumnAttribute), false);
                return (attr as ColumnAttribute).MapName??property.Name;
            }
            else
            {
                return property.Name;
            }
        }

        //public override string ToString()
        //{
        //    if (this.GetType().IsDefined(typeof(ColumnAttribute), false))
        //    {
        //        Attribute attr = Attribute.GetCustomAttribute(this.GetType(), typeof(ColumnAttribute), false);
        //        if (attr != null)
        //        {
        //            return string.Format("{0} likes to eat {1}.", ((ColumnAttribute)attr).MapName,
        //                ((ColumnAttribute)attr).MapName);
        //        }
        //    }
        //    return base.ToString();
        //}

        public static bool IsVerify<T>(T model) where T : class
        {
            var type = model.GetType();
            var properties = type.GetProperties();

            foreach (var propertyInfo in properties)
            {
                var val = propertyInfo.GetValue(model,null);
                var Strval = val?.ToString();
                var attr = Attribute.GetCustomAttribute(propertyInfo, typeof(ColumnAttribute), false) as ColumnAttribute;
                if (attr != null)
                {
                    if (attr.MinLength > 0)
                    {
                        #region MinLength

                        if (!string.IsNullOrWhiteSpace(Strval) && Strval.Length >= attr.MinLength)
                        {
                            Debug.WriteLine(
                                $"Info:{type.Name}--{propertyInfo.Name}--Value MinLength {attr.MinLength}√");
                        }
                        else
                        {
                            Debug.WriteLine(
                                $"Error:{type.Name}--{propertyInfo.Name}--Value MinLength {attr.MinLength}");
                            return false;
                        }

                        #endregion
                    }

                    if (attr.MaxLength > 0)
                    {
                        #region MaxLength
                        if (!string.IsNullOrWhiteSpace(Strval) && Strval.Length <= attr.MaxLength)
                        {
                            Debug.WriteLine(
                                $"Info:{type.Name}--{propertyInfo.Name}--Value MaxLength {attr.MaxLength}√");
                        }
                        else
                        {
                            Debug.WriteLine(
                                $"Error:{type.Name}--{propertyInfo.Name}--Value MaxLength {attr.MaxLength}");
                            return false;
                        }
                        #endregion
                    }
                }
            }

            return false;
        }
    }


}

AttributeUsage：修饰此特性使用范围

IsVerify：集成自定义数据验证

Format：特性与Column特性写法基本差不多，作用是格式化输出

自定义特性必须集成，Attribute类，类名称以“Attribute”结尾

3、调用测试

 [TestMethod]
        public void TestDataVerify()
        {
            var user=new UserInfo();
            user.Pass = "123156";
            user.Status = 3;

            if (ColumnEx.IsVerify(user))
            {

            }
        }

        [TestMethod]
        public void TestFormatOut()
        {
            var user = new UserInfo();
            user.Pass = "123156";
            user.Status = 3;
            user.Total = (decimal)3.556878;
            user.AddDateTime=DateTime.Now;
            var plist = user.GetType().GetProperties();
            foreach (var item in plist)
            {
                Console.WriteLine(item.GetName());
                Debug.WriteLine(item.FormatOutput(item.GetValue(user,null)));
            }
        }