Entity Framwork學習筆記

時間 2019-12-12

標籤 entity framwork 學習筆記简体版

原文原文鏈接

1、First Demo

EF從數據庫生成模型步驟：php

1.數據庫裏有一個UserInfo表：css

2.右擊Model文件夾 - 新建 - Ado.net數據模型：html

3.vue

4.ios

5.c++

6.git

7.es6

8.Modle文件夾會生成兩個類文件：EFTest.cs是數據庫上下文類文件。UserInfo是實體類。web

數據庫上下文類：sql

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

    public partial class EFTest : DbContext
    {
        public EFTest()
            : base("name=MyContext")
        {
        }

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

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
        }
    }
}

View Code

實體類：

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

    [Table("UserInfo")]
    public partial class UserInfo
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int Id { get; set; }

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

        public int? Age { get; set; }

        public DateTime? Birthday { get; set; }
    }
}

View Code

Web.config生成的鏈接字符串：

  <connectionStrings>
    <add name="MyContext" connectionString="data source=.;initial catalog=EFTest;user id=sa;password=123456;MultipleActiveResultSets=True;App=EntityFramework" providerName="System.Data.SqlClient" />
  </connectionStrings>

Controller中使用linq查詢和Lambda方法兩種方式進行查詢：(可鏈接數據庫進行測試Linq寫法與Lambda方式的相互轉換工具下載：LINQPad) LINQPad使用教程>>

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using t2_EFTest.Models;

namespace t2_EFTest.Controllers
{
    public class UserInfoController : Controller
    {
        // GET: /UserInfo/
        public ActionResult Index()
        {
            //MyContext myContext=new MyContext();
            //查詢語法
            //var list = from abc in myContext.UserInfo
            //               select abc;

            //方法語法
            //var list = myContext.UserInfo.Select(u => u);

            //建議：聲明父類型的變量，指向子類型的對象 (面向多態的開始)

            //// DbSet<UserInfo> UserInfo { get; set; } //DbContext dbContext=new MyContext(); ////DbSet<TEntity> Set<TEntity>() //dbContext.Set<UserInfo>();


            IQueryable<UserInfo> list;
            
            //建立上下文對象
            DbContext dbContext=new MyContext();

            //基本查詢
            //list = from userInfo in dbContext.Set<UserInfo>()
            //    select userInfo;

            //單條件查詢
            //list = from userInfo in dbContext.Set<UserInfo>()
            //       where userInfo.Uid>2
            //    select userInfo;

            //多條件
            //list = from userInfo in dbContext.Set<UserInfo>()
            //    where userInfo.Uid > 2 && userInfo.UName.Length > 2
            //    select userInfo;

            //查詢單列
            //var list1 = from userInfo in dbContext.Set<UserInfo>()
            //    select userInfo.Uid;

            //查詢多列
            //var list1 = from useriInfo in dbContext.Set<UserInfo>()
            //            select new UserInfoViewModel()
            //    {
            //        Uid=useriInfo.Uid,
            //        UName=useriInfo.UName
            //    };

            //分頁
            var list1 = from userInfo in dbContext.Set<UserInfo>() 
                            select userInfo;

            list1 = list1.OrderByDescending(u=>u.Uid).Skip(2).Take(3); //先排序，後取數據 分頁是Lambda特有的

            return View(list1);
        }

        public ActionResult Index2()
        {
            DbContext dbContext=new MyContext();

            //基本查詢
            var list1 = dbContext.Set<UserInfo>();

            IQueryable<UserInfo> list;
            //單條件
            list = list1.Where(u => u.Uid > 2);

            //多條件
            //list = list1.Where(u => (u.Uid > 2) || (u.UName.Contains("龍")));
            //list = list1.Where(u => u.Uid > 2)
            //    .Where(u => u.UName.Contains("龍"));

            //查詢自定義列
            //list = list1.select(u => new userinfoviewmodel()   //展現部分列的話，能夠新建一個model類字段爲須要展現的字段
            //{
            //    uid = u.uid,
            //    uname = u.uname
            //});

            return View(list);
        }

    }
}

View中的顯示：

Index：

@using t2_EFTest.Models
@*model IQueryable<t2_EFTest.Models.UserInfo>*@
@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div>
        <table border="1">
            <tr>
                <th>編號</th>
                <th>姓名</th>
            </tr>
            @foreach (var userInfo in Model)
            {
                //var ui = userInfo as UserInfoViewModel;
            <tr>
                <td>@userInfo.Uid</td>
                <td>@userInfo.UName</td>
            </tr>
        }

        </table>
        
    </div>
</body>
</html>

View Code

Index2：

@model IQueryable<t2_EFTest.Models.UserInfo>
@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index2</title>
</head>
<body>
    <div>
        <table border="1">
            <tr>
                <th>編號</th>
                <th>姓名</th>
            </tr>
            @foreach (var userInfo in Model)
            {
                <tr>
                    <td>@userInfo.Uid</td>
                    <td>@userInfo.UName</td>
                </tr>
            }
        </table>
    </div>
</body>
</html>

View Code

表NewsType與NewInfo必須創建外鍵關係才能生成導航屬性：

生成的NewsInfo類：

namespace t2_EFTest.Models
{
    using System;
    using System.Collections.Generic;
    
    public partial class NewsInfo
    {
        public int nid { get; set; }
        public string nTitle { get; set; }
        public int nTid { get; set; }
    
        public virtual NewsType NewsType { get; set; }
    }
}

生成的NewsType類：

namespace t2_EFTest.Models
{
    using System;
    using System.Collections.Generic;
    
    public partial class NewsType
    {
        public NewsType()
        {
            this.NewsInfo = new HashSet<NewsInfo>();
        }
    
        public int tid { get; set; }
        public string tTitle { get; set; }
    
        public virtual ICollection<NewsInfo> NewsInfo { get; set; }
    }
}

導航屬性Controller部分：

using System;
using System.Collections.Generic;
using System.Data.Common;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using t2_EFTest.Models;

namespace t2_EFTest.Controllers
{
    public class NewsInfoController : Controller
    {
        // GET: /NewsInfo/
        public ActionResult Index()
        {
            DbContext dbContext=new MyContext();
            //var list = from newsInfo in dbContext.Set<NewsInfo>()
            //    join typeInfo in dbContext.Set<t2_EFTest.Models.NewsType>() on newsInfo.nTid equals typeInfo.tid
            //    select newsInfo
            //;

            //from後面的in必定要是一個集合類型的對象，才能夠鏈接
            //var list = from newsType in dbContext.Set<NewsType>()
            //    from newsInfo in newsType.NewsInfo
            //    select new
            //    {
            //        NTitle = newsInfo.nTitle,
            //        TTitle = newsType.tTitle
            //    };

            var list = from newsInfo in dbContext.Set<NewsInfo>()
                       select new NewsTypeViewModel //自定義顯示模型來顯示部分字段
                {
                    NTitle=newsInfo.nTitle,
                    TTitle=newsInfo.NewsType.tTitle
                };
            
            return View(list);
        }

    }
}

導航屬性View部分：

@model IQueryable<t2_EFTest.Models.NewsTypeViewModel>
@{
    Layout = null;
}

<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div>
        @Model.GetType()
        <hr/>
        <table border="1">
            @foreach (var newsinfo in Model)
            {
                <tr>
                    <td>@newsinfo.NTitle</td>
                    <td>@newsinfo.TTitle</td>
                </tr>
            }
        </table>
    </div>
</body>
</html>

自定義的NewsTypeViewModel：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace t2_EFTest.Models
{
    public class NewsTypeViewModel
    {
        public string NTitle { get; set; }
        public string TTitle { get; set; }
    }
}

單表增刪改查操做：

View的Index部分：

@using t2_EFTest.Models
@model IQueryable<t2_EFTest.Models.UserInfo>
@{
    Layout = null;
}

<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div>
        @Html.ActionLink("添加","Add","UserInfoCrud")
        <hr/>
        <table border="1">
            <tr>
                <th>編號</th>
                <th>姓名</th>
                <th>修改</th>
                <th>刪除</th>
            </tr>
            @foreach (UserInfo userInfo in Model)
            {
                <tr>
                    <td>@userInfo.Uid</td>
                    <td>@userInfo.UName</td>
                    <td>
                        @Html.ActionLink("修改","Edit","UserInfoCrud",
                        new RouteValueDictionary(new {id=@userInfo.Uid}),null)
                    </td>
                    <td>
                        @Html.ActionLink("刪除",
                        "Remove",
                        "UserInfoCrud",
                        new RouteValueDictionary(new
                        {
                            id=@userInfo.Uid
                        }),null)
                    </td>
                </tr>
            }
        </table>
    </div>
</body>
</html>

Add部分：

@model t2_EFTest.Models.UserInfo
@{
    Layout = null;
}

<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Add</title>
</head>
<body>
    <div>
        @using (Html.BeginForm("Add", "UserInfoCrud", FormMethod.Post))
        {
            <span>姓名：</span>
            @Html.TextBoxFor(u=>u.UName)
            <br/>
            <input type="submit" value="添加"/>
        }
    </div>
</body>
</html>

Edit

@model t2_EFTest.Models.UserInfo
@{
    Layout = null;
}

<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Edit</title>
</head>
<body>
    <div>
        @using (Html.BeginForm("Edit", "UserInfoCrud", FormMethod.Post))
        {
            <span>編號：</span>
            @Model.Uid
            @Html.HiddenFor(u=>u.Uid)
            <br/>
            <span>姓名：</span>
            @Html.TextBoxFor(u=>u.UName)
            <br/>
            <input type="submit" value="修改"/>
        }
    </div>
</body>
</html>

增刪改查Controller部分：

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Data.Entity.Migrations;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;
using t2_EFTest.Models;

namespace t2_EFTest.Controllers
{
    public class UserInfoCrudController : Controller
    {
        DbContext dbContext=new MyContext();
        // GET: /UserInfoCrud/

        public ActionResult Index()
        {
            var list = dbContext.Set<UserInfo>();
            return View(list);
        }

        public ActionResult Add()
        {
            return View();
        }
        [HttpPost]
        public ActionResult Add(UserInfo userInfo)
        {
            dbContext.Set<UserInfo>().Add(userInfo);
            int result=dbContext.SaveChanges();//若是內存中的數據發生了變化，而且但願將這個變化映射到數據庫，須要執行這個方法
            if (result > 0)
            {
                return Redirect(@Url.Action("Index", "UserInfoCrud"));
            }
            else
            {
                return Redirect(@Url.Action("Add"));
            }
        }

        public ActionResult Edit(int id)
        {
            ViewData.Model = dbContext.Set<UserInfo>()
                .Where(u => u.Uid == id).FirstOrDefault();
            return View();
        }
        [HttpPost]
        public ActionResult Edit(UserInfo userInfo)
        {
            dbContext.Set<UserInfo>().AddOrUpdate(userInfo);
            int result = dbContext.SaveChanges();
            if (result > 0)
            {
                return Redirect(Url.Action("Index"));
            }
            else
            {
                return Redirect(Url.Action("Edit", new RouteValueDictionary(new
                {
                    id = userInfo.Uid
                })));
            }
            
        }

        public ActionResult Remove(int id)
        {
            var userInfo = dbContext.Set<UserInfo>()
                .Where(u => u.Uid == id)
                .FirstOrDefault();
            dbContext.Set<UserInfo>().Remove(userInfo);
            dbContext.SaveChanges();

            return Redirect(Url.Action("Index"));
        }
    }
}

EF生成的實體部分：

namespace t2_EFTest.Models
{
    using System;
    using System.Collections.Generic;
    
    public partial class UserInfo
    {
        public int Uid { get; set; }
        public string UName { get; set; }
    }
}

用狀態跟蹤的方式來修改帶導航屬性的數據： (上面AddOrUpdate等這種方式實質仍是用的狀態跟蹤方式，只是作了封裝而已)

View部分：

@model IQueryable<t2_EFTest.Models.NewsInfo>
@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div>
        <table border="1">
            <tr>
                <th>編號</th>
                <th>標題</th>
                <th>分類</th>
                <th>修改</th>
            </tr>
            @foreach (var newsInfo in Model)
            {
                <tr>
                    <td>@newsInfo.nid</td>
                    <td>@newsInfo.nTitle</td>
                    <td>@newsInfo.NewsType.tTitle</td>
                    <td>
                        @Html.ActionLink(
                        "修改",
                        "Edit",
                        "NewsInfoCrud",
                        new RouteValueDictionary(new {id=@newsInfo.nid}),
                        null
                        )
                    </td>
                </tr>
            }
        </table>
    </div>
</body>
</html>

@model t2_EFTest.Models.NewsInfo
@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Edit</title>
</head>
<body>
    <div>
        @using (Html.BeginForm("Edit", "NewsInfoCrud", FormMethod.Post))
        {
            @Model.nid
            @Html.HiddenFor(n=>n.nid)
            <br/>
            @Html.TextBoxFor(n=>n.nTitle)
            <br/>
            <input type="submit" value="修改"/>
        }
    </div>
</body>
</html>

Controller部分：

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using t2_EFTest.Models;

namespace t2_EFTest.Controllers
{
    public class NewsInfoCrudController : Controller
    {
        // GET: /NewsInfoCrud/
        DbContext dbContext=new MyContext();

        public ActionResult Index()
        {
            ViewData.Model = from newsInfo in dbContext.Set<NewsInfo>() 
                                 select  newsInfo;

            return View();
        }

        public ActionResult Edit(int id)
        {
            ViewData.Model= dbContext.Set<NewsInfo>()
                .Where(n => n.nid == id)
                .FirstOrDefault();

            return View();
        }

        [HttpPost]
        public ActionResult Edit(NewsInfo newsInfo)
        {
            //使用狀態方式進行修改
            dbContext.Set<NewsInfo>().Attach(newsInfo);
            //dbContext.Entry(newsInfo).State = EntityState.Modified; //這種方式只適合修改全部字段，包括外鍵字段，否則會報錯
            dbContext.Entry(newsInfo).Property("nTitle").IsModified = true; //這種方式適合修改部分列
            dbContext.Entry(newsInfo).Property("nTitle").CurrentValue = newsInfo.nTitle;
            dbContext.SaveChanges();

            return Redirect(Url.Action("Index"));
        }
    }
}

2、延遲加載 (用的時候纔去拿數據)

IQueryable<T>可使用匿名錶達式

延遲加載View部分：

@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div>
        @*@foreach (var userInfo in ViewBag.list)
        {
            @userInfo.Uid
        }*@
        
        <hr/>
       @* @foreach (var userInfo in ViewBag.list)
        {
            @userInfo.Uid
        }*@
        <hr/>
        
       @* @foreach (var userInfo in ViewBag.list2)
        {
            @userInfo.Uid
        }*@
        
        @*@foreach (var newsInfo in ViewBag.list3)
        {
            @newsInfo.NewsType.tid
        }*@
        

    </div>
</body>
</html>

延遲加載controller部分：

using System;
using System.Collections.Generic;
using System.Data.Common.CommandTrees;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using t2_EFTest.Models;

namespace t2_EFTest.Controllers
{
    public class DelayLoadController : Controller
    {
        //
        // GET: /DelayLoad/

        public ActionResult Index()
        {
            DbContext dbContext=new MyContext();

            //延遲加載：若是不使用數據，則只是拼接sql語句，不會將結果集拿到內存中來

            //IQueryable<UserInfo> list = dbContext.Set<UserInfo>()
            //    .OrderByDescending(u => u.Uid)//默認會將lambda表達式封裝成Expression對象，而調用IQueryable<T>的方法
            //    .Skip(2)
            //    .Take(3);
            //ViewBag.list = list.ToList(); //結尾增長.ToList或FirstOrDefault()來切換爲非延遲加載，直接加載到內存中。

            IEnumerable<UserInfo> list2 = dbContext.Set<UserInfo>()
                .AsEnumerable()
                .OrderByDescending(u => u.Uid)
                .Skip(2)
                .Take(3);
            ViewBag.list2 = list2;

            //導航屬性默認也會使用延遲加載
            IQueryable<NewsInfo> list3 = dbContext.Set<NewsInfo>();
            ViewBag.list3 = list3.Include(n=>n.NewsType).ToList();

            return View();
        }

    }
}