一、获取EF

 1.打开NuGet程序包管理器控制台

 2.选择默认项目（要导入EF的项目），输入命令：Install-Package EntityFramework

3.若导入成功，在引用中会有以下两个引用

二、添加实体数据模型 

 1.添加新项，选择ADO.NET 实体数据模型

 2.选择Code First（也可以选择其他两种模式DB First和Model First)

ps:三者区别，推荐博文：https://blog.csdn.net/u010191243/article/details/44755977?utm_source=copy

 3.选择要建立模型的数据库，连接字符串可以选择自动生成或者手动设置

4.选择要生成模型的表和视图 

 5.项目中会自动生成一个派生于DbContext的文件和各个表模型类

三、生成文件的简单介绍 

1.数据库表信息 

CREATE TABLE [dbo].[T_EF]
(
	[ID] [numeric](18, 0) IDENTITY(1,1) NOT NULL primary key,
	[Name] [nchar](10) NULL,
	[Age] [tinyint] NULL,
	[Location] [nchar](10) NULL
)

2. DbContext

namespace EFConsole
{
    using System;
    using System.Data.Entity;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Linq;

    public partial class BridgeContext : DbContext
    {
        /// <summary>
        /// 利用连接字符串连接数据库
        /// </summary>
        public BridgeContext(string connStr) : base(connStr)
        {
        }

        /// <summary>
        /// 利用App.config中配置的字符串连接数据库
        /// </summary>
        public BridgeContext() : base("name=BridgeDb")
        {
        }

        public virtual DbSet<T_EF> T_EF { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<T_EF>()
                .Property(e => e.ID)
                .HasPrecision(18, 0);

            modelBuilder.Entity<T_EF>()
                .Property(e => e.Name)
                .IsFixedLength();

            modelBuilder.Entity<T_EF>()
                .Property(e => e.Location)
                .IsFixedLength();
        }
    }
}

3.App.config文件 

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <!--选择生成带密码时的连接字符串-->
    <add name="BridgeDb" connectionString="Server=.;Initial Catalog=Bridge;User ID=sa;Password=123" providerName="System.Data.SqlClient" />
    <!--选择生成不带密码时的连接字符串-->
    <add name="BridgeContext" connectionString="data source=PC-20181123XOVS\BRIDGE;initial catalog=Bridge;persist security info=True;user id=sa;MultipleActiveResultSets=True;App=EntityFramework" providerName="System.Data.SqlClient" />
  </connectionStrings>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
  </startup>
  <entityFramework>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>
</configuration>

4.表文件 

namespace EFConsole
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    /// <summary>
    /// 指定表名
    /// </summary>
    [Table("T_EF")]
    public class T_EF
    {
        /// <summary>
        /// [主键(每个表必须要有主键),表示是自增列]
        /// </summary>
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public decimal ID { get; set; }

        /// <summary>
        /// [指定对应的列名,限定列的字符长度]
        /// </summary>
        [Column("Name"), StringLength(10)]
        public string Name { get; set; }

        /// <summary>
        /// 可空类型指定
        /// </summary>
        public byte? Age { get; set; }

        [StringLength(10)]
        public string Location { get; set; }
    }
}

四、对数据库的增删改查 

1.增 

using (var bridgeContext = new BridgeContext())
{
    //添加一个对象
    T_EF t_EF = bridgeContext.T_EF.Add(new T_EF() { Name = "RB" });
    //将修改后的保存到数据库
    bridgeContext.SaveChanges();
}

2.查 

//根据主键查询
T_EF t_EF1 = bridgeContext.T_EF.Find(1);

//根据TSQL查询
DbSqlQuery<T_EF> dbSqlQuery = bridgeContext.T_EF.SqlQuery("select * from [T_EF] where [ID] = {0}", 2);

3.改 

//修改数据，需先查出实体，再修改保存
T_EF t_EF1 = bridgeContext.T_EF.Find(1);
t_EF1.Location = "GD";
bridgeContext.SaveChanges();

4.删 

//删除数据也需先查出后删除再保存
DbSqlQuery<T_EF> dbSqlQuery = bridgeContext.T_EF.SqlQuery("select * from [T_EF] where [ID] = {0}", 2);
bridgeContext.T_EF.RemoveRange(dbSqlQuery);
bridgeContext.SaveChanges();