Entity Framework系列之DataBase First

第一步 新建数据库和表

USE [TestDB]
GO
/****** Object:  Table [dbo].[T_User]    Script Date: 01/14/2015 20:27:52 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[T_User](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](50) NULL,
    [Password] [nchar](10) NULL,
 CONSTRAINT [PK_T_User] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO

第二步 ADO.NET实体数据模型

新建ADO.NET实体数据模型

程序自动生成以下文件

TestModel.edmx

TestModel.Context.tt

TestModel.Context.tt是生成数据操作实体类的模板

namespace EFDEMO1
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;
    
    public partial class TestDBEntities : DbContext
    {
        public TestDBEntities()
            : base("name=TestDBEntities")  //TestDBEntities为App.config中的数据库连接字符串
        {
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
    
        public DbSet<T_User> T_User { get; set; }
    }
}

TestModel.Designer.cs

TestModel.edmx.diagram

TestModel.tt

TestModel.tt模板是生成T_User实体类的模板

namespace EFDEMO1
{
    using System;
    using System.Collections.Generic;
    
    public partial class T_User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Password { get; set; }
    }
}

修改数据库

当修改数据库对象（如表），只需要在TestModel.edmx界面上右键点击从数据库更新模型，更新完成后保存即可自动生成相关代码（如实体类）。

第三步 增删改查

using System;
using System.Data;
using System.Linq;
using System.Windows.Forms;

namespace EFDEMO1
{
    public partial class Form1 : Form
    {
        TestDBEntities entity = new TestDBEntities();
        
        public Form1()
        {
            InitializeComponent();
        }

        /// <summary>
        /// 新增
        /// </summary>
        private void Add()
        {
            T_User model = new T_User()
            {
                Name = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss")
            };
            entity.T_User.Add(model);
            entity.SaveChanges();
            Query();
        }

        /// <summary>
        /// 删除
        /// </summary>
        private void Delete()
        {
            if (listBox1.SelectedItem == null)
            {
                return;
            }
            int id = Convert.ToInt32(listBox1.SelectedItem.ToString().Split('-')[0]);
            T_User model = entity.T_User.Where(a => a.Id == id).FirstOrDefault();
            if (model != null)
            {
                entity.Entry(model).State = EntityState.Deleted;
                entity.SaveChanges();
                Query();
            }
        }

        /// <summary>
        /// 修改
        /// </summary>
        private void Edit()
        {
            if (listBox1.SelectedItem == null)
            {
                return;
            }
            int id = Convert.ToInt32(listBox1.SelectedItem.ToString().Split('-')[0]);
            T_User model = entity.T_User.Where(a => a.Id == id).FirstOrDefault();
            if (model != null)
            {
                model.Name = DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss");
                entity.Entry(model).State = EntityState.Modified;
                entity.SaveChanges();
                Query();
            }
        }

        /// <summary>
        /// 查询
        /// </summary>
        private void Query()
        {
            listBox1.Items.Clear();
            var expr = from p in entity.T_User select p;
            foreach (var item in expr)
            {
                listBox1.Items.Add(string.Format("{0}-{1}", item.Id, item.Name));
            }
        }

        private void toolStripButton1_Click(object sender, EventArgs e)
        {
            Add();
        }

        private void toolStripButton4_Click(object sender, EventArgs e)
        {
            Edit();
        }

        private void toolStripButton3_Click(object sender, EventArgs e)
        {
            Delete();
        }

        private void toolStripButton2_Click(object sender, EventArgs e)
        {
            Query();
        }
    }
}