EntityFramework-DBFirst-重新生成后写的验证消失（解决办法）

namespace PMS.DataProvider.EntityFramework
{
    using System;
    using System.Collections.Generic;
    
    public partial class M_Managers
    {
        public string UserName { get; set; }
        public string NickName { get; set; }
        public string PassWord { get; set; }
        public string HeadImg { get; set; }
        public int Age { get; set; }
        public bool IsMale { get; set; }
        public string Email { get; set; }
        public string Mobile { get; set; }
        public string Address { get; set; }
        public string Signature { get; set; }
        public string Roles { get; set; }
        public string Description { get; set; }
        public System.DateTime CreateDate { get; set; }
        public string CreateUser { get; set; }
        public System.DateTime LastLoginDate { get; set; }
        public int LoginTimes { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PMS.DataProvider.EntityFramework
{
    [MetadataType(typeof(M_ManagersMetadata))]
    public partial class M_Managers
    {

    }

    public class M_ManagersMetadata
    {
        [Display(Name = "用户名")]
        [Required(ErrorMessage = "*")]
        [StringLength(50, ErrorMessage = "字符长度应在6-50之间", MinimumLength = 6)]
        public string UserName { get; set; }

        [Display(Name = "显示名")]
        [Required(ErrorMessage = "*")]
        [StringLength(50, ErrorMessage = "字符长度应在6-50之间", MinimumLength = 6)]
        public string NickName { get; set; }

        [Display(Name = "密码")]
        [Required(ErrorMessage = "*")]
        [DataType(DataType.Password)]
        [StringLength(50, ErrorMessage = "字符长度应在6-50之间", MinimumLength = 6)]
        public string PassWord { get; set; }

        [Display(Name = "头像")]
        [DataType(DataType.ImageUrl)]
        public string HeadImg { get; set; }

        [Display(Name = "年龄")]
        [Range(10, 120, ErrorMessage = "年龄应在10-120之间")]
        public int Age { get; set; }

        [Display(Name = "性别")]
        public bool IsMale { get; set; }

        [Display(Name = "邮箱")]
        [Required(ErrorMessage = "*")]
        [DataType(DataType.EmailAddress)]
        [EmailAddress(ErrorMessage = "邮箱格式不正确")]
        [StringLength(50, ErrorMessage = "字符长度应在6-50之间", MinimumLength = 6)]
        public string Email { get; set; }

        [Display(Name = "手机")]
        [Required(ErrorMessage = "*")]
        public string Mobile { get; set; }

        [Display(Name = "地址")]
        public string Address { get; set; }

        [Display(Name = "签名")]
        public string Signature { get; set; }

        [Display(Name = "角色")]
        public string Roles { get; set; }

        [Display(Name = "描述")]
        [DataType(DataType.MultilineText)]
        public string Description { get; set; }

        [Display(Name = "创建日期")]
        [DataType(DataType.DateTime, ErrorMessage = "日期格式不正确")]
        public System.DateTime CreateDate { get; set; }

        [Display(Name = "创建人")]
        public string CreateUser { get; set; }

        [Display(Name = "最后登录日期")]
        [DataType(DataType.Date, ErrorMessage = "日期格式不正确")]
        public System.DateTime LastLoginDate { get; set; }

        [Display(Name = "登录次数")]
        public int LoginTimes { get; set; }
    }
}

    [MetadataType(typeof(M_ManagersMetadata))]//给新建的部分类指定要关联的元数据类
    public partial class M_Managers//这是新建的部分类（里面是空的，啥也不写），注意要与EF生成的类一样，包括类名称和命名空间
    {

    }

    public class M_ManagersMetadata//新建一个元数据类
    {
         //这里写Model验证
        [Display(Name = "用户名")]
        [Required(ErrorMessage = "*")]
        [StringLength(50, ErrorMessage = "字符长度应在6-50之间", MinimumLength = 6)]
        public string UserName { get; set; }
 　 }