如何避免在EF自動產生的model中的DataAnnotation被覆蓋掉

相信很多人剛接觸EF+MVC的時候，會有這個疑問，就是當我們在model類中加驗證資訊的時候，會在重建model的時候被重寫掉。這裡介紹一個方法：

比如我有個Employee類是從資料庫中產生到model中的，我們可以在Models檔案夾中建立一個部分類名稱與Employee類同名（注意：該類的命名空間必須與自動產生的類屬於同一個命名空間），類內容為空白的就可以，然後在建立的部分類下方再建立一個類（EmployeeMetaData),類中中加上我們需要驗證的列與驗證資訊，然後需要將

[MetadataType(typeof(EmployeeMetaData))]加在建立的Employee類名上方

這時我們在view頁面中不用更改代碼。這樣當我們重建model的時候，我們自己定義的部分類Employee就不會受影響了。

下面是範例代碼：

從資料庫中產生的Employee：

//------------------------------------------------------------------------------// <auto-generated>//     This code was generated from a template.////     Manual changes to this file may cause unexpected behavior in your application.//     Manual changes to this file will be overwritten if the code is regenerated.// </auto-generated>//------------------------------------------------------------------------------namespace ValidationDemo{    using System;    using System.Collections.Generic;        public partial class Employee    {        public Employee()        {            this.Employees1 = new HashSet<Employee>();            this.Orders = new HashSet<Order>();            this.Territories = new HashSet<Territory>();        }            public int EmployeeID { get; set; }        public string LastName { get; set; }        public string FirstName { get; set; }        public string Title { get; set; }        public string TitleOfCourtesy { get; set; }        public Nullable<System.DateTime> BirthDate { get; set; }        public Nullable<System.DateTime> HireDate { get; set; }        public string Address { get; set; }        public string City { get; set; }        public string Region { get; set; }        public string PostalCode { get; set; }        public string Country { get; set; }        public string HomePhone { get; set; }        public string Extension { get; set; }        public byte[] Photo { get; set; }        public string Notes { get; set; }        public Nullable<int> ReportsTo { get; set; }        public string PhotoPath { get; set; }        public Nullable<int> COL1 { get; set; }            public virtual ICollection<Employee> Employees1 { get; set; }        public virtual Employee Employee1 { get; set; }        public virtual ICollection<Order> Orders { get; set; }        public virtual ICollection<Territory> Territories { get; set; }    }}

建立一個部分類，命名為Employee：

using System;using System.Collections.Generic;using System.ComponentModel.DataAnnotations;using System.Linq;using System.Web;namespace ValidationDemo{    [MetadataType(typeof(EmployeeMetaData))]    public partial class Employee    {    }    public partial class EmployeeMetaData    {        public int EmployeeID { get; set; }        [Required]        public string LastName { get; set; }        public string FirstName { get; set; }        public string Title { get; set; }        public string TitleOfCourtesy { get; set; }        public Nullable<System.DateTime> BirthDate { get; set; }        public Nullable<System.DateTime> HireDate { get; set; }        public string Address { get; set; }        public string City { get; set; }        public string Region { get; set; }        public string PostalCode { get; set; }        public string Country { get; set; }        public string HomePhone { get; set; }        public string Extension { get; set; }        public byte[] Photo { get; set; }        public string Notes { get; set; }        public Nullable<int> ReportsTo { get; set; }        public string PhotoPath { get; set; }        public Nullable<int> COL1 { get; set; }    }}

參考文檔：
http://www.asp.net/mvc/tutorials/older-versions/models-(data)/validation-with-the-data-annotation-validators-cs

OK,大功告成。