EntityFramework使用总结(与MVC4.0实现CURD操作)

朱雀 2021-11-22 06:20 186阅读 0赞

本篇文介绍一下Entity Framework Code First的简单用法，通过一个学生信息的增删查改来学习Entity Framework的使用及与存储过程的交互。我也是学习Entity Framework新手，有说的不对地方欢迎指正。

本文使用的开发环境为VS2010(sp1)+MVC4.0+EF5.0。

**一、我们新建一个空MVC空项目**

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添加EntityFramework.dll的引用。

**二、修改配web.config置文件(web.config为根目录下的)**

添加EntityFramework配置和数据库连接字符串。

**三、在Models文件夹下新建Students.cs和DbHelper.cs**

1、Students为学生信息实体类，并关联数据库表和其他一些属性说明，代码如下

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using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.ComponentModel.DataAnnotations;
    
    namespace MVCEF.Models
    {
        [Table("tb_Students", Schema = "dbo")]//关联数据表 dbo.tb_Students
        public class Students
        {
            [Key]
            public string Num { get; set; }
            [MaxLength(10),Required(ErrorMessage="姓名不能为空")]
            [Column(TypeName = "nvarchar")]
            public string Name { get; set; }
            public int Age { get; set; }
            [MaxLength(10)]
            [Column(TypeName = "varchar")]
            public string Sex { get; set; }
            [MaxLength(50)]
            public string Class { get; set; }
        }
    }

说明：用属性Key说明的字段如果是int类型，EF会默认该字段对应的数据库表字段是自增的，好像是这样的，说的不对的请纠正。

2、DbHelper.cs主要创建数据库上下文，代码如下：

using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    
    namespace MVCEF.Models
    {
        public class DbHelper:DbContext
        {
            public DbHelper()
                : base("strConn")
            {
                //自动创建表，如果Entity有改到就更新到表结构
                Database.SetInitializer<DbHelper>(new MigrateDatabaseToLatestVersion<DbHelper, ReportingDbMigrationsConfiguration>());
            }
            public DbSet<Students> Students { get; set; }
        }
        internal sealed class ReportingDbMigrationsConfiguration : DbMigrationsConfiguration<DbHelper>
        {
            public ReportingDbMigrationsConfiguration()
            {
                AutomaticMigrationsEnabled = true;//任何Model Class的修改將會直接更新DB
                AutomaticMigrationDataLossAllowed = true;
            }
        }
    }

说明：这里还需要请用System.Data.Entity.DLL

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要不然会报如下的一个错误：

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四、我们创建表tb\_Students和存储过程proc\_1

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CREATE TABLE [dbo].[tb_Students](
        [Num] [varchar](128) NOT NULL,
        [Name] [nvarchar](10) NOT NULL,
        [Age] [int] NULL,
        [Sex] [varchar](10) NULL,
        [Class] [nvarchar](50) NULL,
    PRIMARY KEY CLUSTERED 
    (
        [Num] 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

tb\_Students

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create proc proc_1
    @Num varchar(128),
    @Name varchar(50)
    as 
    select * from dbo.tb_Students where Num=@Num and Name=@Name

proc\_1

五、HomeController.cs调用EF方法实现增删改查。

方法都比较简单，这里就不做详细说明了

using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Web.Mvc;
    using MVCEF.Models;
    using System.Data;
    using System.Data.SqlClient;
    
    namespace MVCEF.Controllers
    {
        public class HomeController : Controller
        {
            DbHelper db = new DbHelper();
            private static List<Students> listStu = new List<Students>()
            {
                new Students(){Num="s0001",Name="张三",Age=19,Sex="man",Class="计算机1班"},
                new Students(){Num="s0002",Name="李四",Age=20,Sex="man",Class="计算机1班"},
                new Students(){Num="s0003",Name="王五",Age=18,Sex="man",Class="计算机1班"},
                new Students(){Num="s0004",Name="小红",Age=17,Sex="women",Class="计算机'\"1班"},
            };
            //
            // GET: /Home/
    
            public ActionResult Index()
            {
                //如果没有数据初始化数据
                if (db.Students.Count() == 0)
                {
                    listStu.ForEach(it =>
                        {
                            db.Students.Add(it);
                        });
                    db.SaveChanges();
                }
                List<Students> lst = db.Students.ToList();
                //实现2：sql语句实现
                //List<Students> lst = db.Students.SqlQuery("select * from tb_Students").ToList();
                //与存储过程交互
               // var result = db.Database.SqlQuery<Students>("exec proc_1 @p0,@p1", "s0001","张三1").ToList();
                return View(lst);
            }
            public ActionResult Add()
            {
                return View(new Students());
            }
            [HttpPost]
            public ActionResult Add(Students stu)
            {
                string Message = string.Empty;
                if (db.Students.Where(it => it.Num == stu.Num).FirstOrDefault()!=null)
                {
                    Message = "学号已经存在";
                    ViewBag.Msg = Message;
                    return View();
                }
                db.Students.Add(stu);
                db.SaveChanges();
                return RedirectToAction("Index","Home");
            }
    
            public ActionResult edit(string id)
            {
                var stu=db.Students.Where(it => it.Num == id).FirstOrDefault();
                return View(stu);
            }
            [HttpPost]
            public ActionResult edit(Students stu, FormCollection form,string id)
            {
                stu.Num = id;
                db.Entry(stu).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index", "Home");
            }
            //删除
            public ActionResult Del(string id)
            {
                /*方法1
                var stu = db.Students.Where(it => it.Num == id).FirstOrDefault();
                db.Entry(stu).State = EntityState.Deleted;
                db.SaveChanges();
                 */
                //方法2
                string strsql = "delete from tb_Students where Num=@Num";
                SqlParameter[] paras =
               {
                   new SqlParameter("@Num",SqlDbType.NVarChar,128)
               };
                paras[0].Value=id;
                db.Database.ExecuteSqlCommand(strsql, paras);
                db.SaveChanges();
                return RedirectToAction("Index", "Home");
            }
        }
    }

**六、EF与存储过程交互**

EF与存储过程交互详见Index方法： var result = db.Database.SqlQuery<Students>("exec proc_1 @p0,@p1", "s0001","张三1").ToList();
    其中@p0,@p1为传入存储过程中的参数(依次对应存储过程参数@Num和@Name)。 我们在使用EF调用存储过程的时候传入的参数为@p0,@p1,@p2,@p3 依此排列下去(蛋疼不知道为啥这样设计) 但是如何获取存储过程的返回值和out参数我还没有找到，如果你知道希望能留下你的答案，共同学习。

**如果你有什么更好的关于EF的学习资料欢迎共享共同学习**

**[点击][Link 1]下载源码**

**每天学习一点点，每天进步一点点**

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[ContractedBlock.gif]: http://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
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[Link 1]: http://files.cnblogs.com/lc-chenlong/MVCEF.zip