【EF】EntityFramework DBFirst的使用

一、前言

       久聞EF大名，之前做C/S產品用的是Dapper對SqlLite進行ORM。然後接觸公司授權系統後發現用的是EntityFramework對SQLSever進行ORM。授權系統里用的是DBFirst，增刪查改使用Linq To Entity，覺得非常方便。本篇篇幅較短，老司機可直接略過

二、添加EF       

        Step1：添加“新建項”，起個名稱，添加ADO.NET實體數據模型；

         Step2：選擇模型類型，來自資料庫的EF設計器；

         Step3：選擇數據連接，新建連接，選擇要使用的資料庫類型；預設SQLSever；

         Step4：測試連接資料庫；

         Step5：選擇EF版本；

         Step6：選擇要實體化的表，點擊完成。

三、操作

       經過上述操作會產生三個文件：

        1. EntityModel.Context.tt (上下文，所有class的DBSet集合都在這個文件下的.cs文件中)

        2. EntityModel.tt       (每個表映射後的class都放在這個文件下麵)

        3. EntityModel.edmx (可視化的表設計器)

        假設連接的資料庫下有三個表：AgencyInfo,ContractInfo,CustomerInfo。那麼EntityModel.tt下就會有三個對應的.cs文件：

//------------------------------------------------------------------------------
// <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>
//------------------------------------------------------------------------------

using System;
using System.Collections.Generic;

namespace HHH
{
    public partial class AgencyInfo
    {
        public System.Guid ID { get; set; }
        public string UnitName { get; set; }
        public string Phone { get; set; }
        public string Address { get; set; }
        public string comments { get; set; }
        public Nullable<System.DateTime> CreatTime { get; set; }
        public Nullable<int> ShowFlag { get; set; }
    }
    
}

//------------------------------------------------------------------------------
// <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>
//------------------------------------------------------------------------------

using System;
using System.Collections.Generic;

namespace HHH
{
    public partial class ContractInfo
    {
        public System.Guid ID { get; set; }
        public string Title { get; set; }
        public string Comment { get; set; }
        public Nullable<System.DateTime> CreateDate { get; set; }
    }
    
}

//------------------------------------------------------------------------------
// <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>
//------------------------------------------------------------------------------

using System;
using System.Collections.Generic;

namespace HHH
{
    public partial class CustomerInfo
    {
        public System.Guid ID { get; set; }
        public string Name { get; set; }
        public string ContactInfo { get; set; }
        public string Address { get; set; }
        public string Comments { get; set; }
        public string Email { get; set; }
        public string MobilePhone { get; set; }
        public string province { get; set; }
        public string City { get; set; }
        public string Type { get; set; }
        public Nullable<System.DateTime> CreateDate { get; set; }
    }
    
}

         那麼EntityModel.Context.tt是這樣的：

//------------------------------------------------------------------------------
// <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>
//------------------------------------------------------------------------------

using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;

namespace HHH
{
    public partial class MyEntities: DbContext
    {
        public MyEntities()
            : base("name=MyEntities")
        {
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
          
        public DbSet<ContractInfo> ContractInfoes { get; set; }
        public DbSet<CustomerInfo> CustomerInfoes { get; set; }
        public DbSet<AgencyInfo> AgencyInfoes { get; set; }

    }
}

           需要對錶對象操作時，首先要：

private MyEntities dbContext = new MyEntities();

             需要對哪個表操作，就dbContext.ContractInfoes或者dbContext.CustomerInfoes這樣找到數據集合，然後用Linq去操作，最後別忘dbContext.SaveChanges()保存修改即可。