EF5&MVC4 学习一、建立新的Contoso University Application,并建立Model Class 生成对应的database

时间 2019-11-12

标签 ef5&mvc4 mvc 学习建立新的 contoso university application model class 生成对应 database 繁體版

原文原文链接

参考：http://www.asp.net/mvc/tutorials/getting-started-with-ef-5-using-mvc-4/creating-an-entity-framework-data-model-for-an-asp-net-mvc-applicationcss

Create The Contoso University Web Applicationhtml

Contoso University sample web applicatioin 是一个使用MVC4 & EF5 & VS2012建立的Sample网站。网站功能包括：学生入学，课程选择，做业布置。这一系列的教程会教咱们如何创建这个网站。jquery

Code First web

在Entiry Framework中，咱们有三种处理数据的方法：Database First,Model First,and Code First.这个教程中，咱们使用Code First。关于这三种之间的差异以及具体该选择哪一种，能够参考Entity Framework Development Workflows。数据库

The Contoso University Web Applicationmvc

功能：用户能够查看，更新学生、课程、教师信息。app

这个Application的UI页面，是系统自动生成的Template。因此咱们能够关注于怎么去用Entity Framework.以后咱们再用Kendo UI去更新咱们的UI。asp.net

准备(Prerequisits): Windows Azure SDK http://go.microsoft.com/fwlink/?LinkId=254364ide

一，建立一个MVC WEB Application学习

Create a new project named “ContosoUniversity”,Using .NET Framework 4.5

网站样式设置（Set Up The Site Style）

咱们会对网站的site menu,layout和home page作出一些更新

Views\Shared\_Layout.cshtml：更改母版页的标题，增长一些链接

<!DOCTYPE html>
<html lang="zh">
    <head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
        <meta charset="utf-8" />
        <title>@ViewBag.Title - Contoso University</title>
        <link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />
        <meta name="viewport" content="width=device-width" />
        @Styles.Render("~/Content/css")
        @Scripts.Render("~/bundles/modernizr")
    </head>
    <body>
        <header>
            <div class="content-wrapper">
                <div class="float-left">
                    <p class="site-title">@Html.ActionLink("Contoso University", "Index", "Home")</p>
                </div>
                <div class="float-right">
                    <section id="login">
                        @Html.Partial("_LoginPartial")
                    </section>
                    <nav>
                        <ul id="menu">
                            <li>@Html.ActionLink("首頁", "Index", "Home")</li>
                            <li>@Html.ActionLink("關於", "About", "Home")</li>
                            <li>@Html.ActionLink("學生", "Student", "Home")</li>
                             <li>@Html.ActionLink("課程", "Course", "Home")</li>
                             <li>@Html.ActionLink("教師", "Instructors", "Home")</li>
                            <li>@Html.ActionLink("部門", "Departments", "Home")</li>
                        </ul>
                    </nav>
                </div>
            </div>
        </header>
        <div id="body">
            @RenderSection("featured", required: false)
            <section class="content-wrapper main-content clear-fix">
                @RenderBody()
            </section>
        </div>
        <footer>
            <div class="content-wrapper">
                <div class="float-left">
                    <p>&copy; @DateTime.Now.Year - Contoso University</p>
                </div>
            </div>
        </footer>

        @Scripts.Render("~/bundles/jquery")
        @RenderSection("scripts", required: false)
    </body>
</html>

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Views\Home\Index.cshtml：只保留如下这些：

Controllers\HomeController.cs：更改ViewBage.Message的内容：

 public ActionResult Index()
        {
            ViewBag.Message = "Welcome to Contoso University";

            return View();
        }

Ctrl+F5运行：

二，为Contoso University application 建立实体数据模型(Entity Data Model)

Model 中添加Entity Class:

1,添加Student.cs类：

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

namespace ContosoUniversity.Models
{
    public class Student
    {
        public int StudentID { get; set; }
        public string LastName { get; set; }
        public string FirstMidName { get; set; }
        public DateTime EnrollmentDate { get; set; }

        public virtual ICollection<Enrollment> Entrollments { get; set; }
    }
}

View Code

2，添加Course.cs类

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;

namespace ContosoUniversity.Models
{
    public class Course
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int CourseID { get; set; }
        public string Title { get; set; }
        public int Credits { get; set; }

        public virtual ICollection<Enrollment> Enrollments { get; set; }

    }
}

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3，添加Enrollment.cs类

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

namespace ContosoUniversity.Models
{
    public enum Grade
    {
        A, B, C, D, F
    }
    public class Enrollment
    {

        public int EnrollmentID { get; set; }
        public int CourseID { get; set; }
        public int StudentID { get; set; }
        public Grade? Grade { get; set; }

        public virtual Course Course { get; set; }
        public virtual Student Student { get; set; }
    }
}

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三，建立数据上下文类（Create the Database Context）

数据库上下文类是Model 中的实体数据模型(Data Model)和Entity Framework 之间的桥梁

Database context class类继承自System.Data.Entity.DbContext 类，这里面你须要指明哪些实体包含在data model 中。你一样能够自定义某些特定的Entity Framework behavior. 这个Project 中DbContext的类名为SchoolContext

添加DAL文件夹，而后添加SchoolContext类：

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

namespace ContosoUniversity.Models
{
    public enum Grade
    {
        A, B, C, D, F
    }
    public class Enrollment
    {

        public int EnrollmentID { get; set; }
        public int CourseID { get; set; }
        public int StudentID { get; set; }
        public Grade? Grade { get; set; }

        public virtual Course Course { get; set; }
        public virtual Student Student { get; set; }
    }
}

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DbContext类为每个实体集（entity set）建立了一个DbSet属性

每个实体集对应database中的一张table,每个实体对应

OnModelCreating方法中的modelBuilder.Conventions.Remove 防止表中的数据以复数(Students,Courses,Enrollments)命名。

四，SQL Server Express LocalDB

.mdf为后缀的database文件，是一个单独的文件放置于项目中的App_Data文件夹中。LocalDB不被推荐使用在web application中由于它不会和IIS一块儿工做。在VS2012以及之后的版本中，LocalDB被默认安装在VS中。

若是你是用.mdf存贮数据的话，须要更新web.config，添加连接字符串以下：

 <add name="SchoolContext" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=ContosoUniversity;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\ContosoUniversity.mdf" providerName="System.Data.SqlClient" />

默认状况下，Entiry Framework 会在webconfig中寻找和类名DbContext同名的链接字符串(这里是SchoolContext)，链接字符串就会指定APP_Data中一个命名为ContosoUniversity.mdf的数据文件

若是你不手动在webconfig中添加这个链接字符串，Entity Framework就会自动给你添加一个链接字符串，可是这个database文件不会再App_Data文件中。

ConnectionStrings 中包含有名字为DefaultConnection的默认的字符串链接，这个链接是用于Membership database的。在这个教程中咱们暂时不会用到membership database. 这两种链接的不一样之处就是数据库名称(database name)和属性值(attribute value).

5、设置并执行Code First Migration . Set up and Execute a Code First Migration

在咱们开始开发项目的时候，咱们须要频繁的更新Data Mode中的实体类(entity class )，每一次更新之后，Model 中的字段就和database中的字段不一致了。

因此咱们须要配置Entity Framework 来自动drop 或者re-create database来和model 中的实体类同步。这样drop的方法来更新，在开发中咱们用的都是测试数据不会有什么问题，可是一旦部署到正式环境，咱们就不能用这种方法去同步mode和database了。 Code First的Migrations功能可让咱们更新数据库结果，而且不用去drop 和 re-create database。

5.1 Enable Code First Migrations

1,Package Manager Console:

2,输入命令：PM>enable-migrations -contexttypename SchoolContext

启用成功，而且建立了Migrations文件夹以及Configurations.cs文件

当database在被created的时候以及每一次从Model中进行同步更新的时候，Configuration.cs中的Seed方法就会被调用。

Seed方法可让咱们可以在Code First建立或者更新database之后，插入测试数据。

5.2 Set up Seed Method

namespace ContosoUniversity.Migrations
{
    using System;
    using System.Collections.Generic;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    using System.Linq;
    using ContosoUniversity.Models;

    internal sealed class Configuration : DbMigrationsConfiguration<ContosoUniversity.DAL.SchoolContext>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = false;
        }

        protected override void Seed(ContosoUniversity.DAL.SchoolContext context)
        {
            //  This method will be called after migrating to the latest version.

            //  You can use the DbSet<T>.AddOrUpdate() helper extension method 
            //  to avoid creating duplicate seed data. E.g.
            //
            //    context.People.AddOrUpdate(
            //      p => p.FullName,
            //      new Person { FullName = "Andrew Peters" },
            //      new Person { FullName = "Brice Lambson" },
            //      new Person { FullName = "Rowan Miller" }
            //    );
            //

            var students = new List<Student>{
           new Student { FirstMidName = "Carson",   LastName = "Alexander", 
                    EnrollmentDate = DateTime.Parse("2010-09-01") },
                new Student { FirstMidName = "Meredith", LastName = "Alonso",    
                    EnrollmentDate = DateTime.Parse("2012-09-01") },
                new Student { FirstMidName = "Arturo",   LastName = "Anand",     
                    EnrollmentDate = DateTime.Parse("2013-09-01") },
                new Student { FirstMidName = "Gytis",    LastName = "Barzdukas", 
                    EnrollmentDate = DateTime.Parse("2012-09-01") },
                new Student { FirstMidName = "Yan",      LastName = "Li",        
                    EnrollmentDate = DateTime.Parse("2012-09-01") },
                new Student { FirstMidName = "Peggy",    LastName = "Justice",   
                    EnrollmentDate = DateTime.Parse("2011-09-01") },
                new Student { FirstMidName = "Laura",    LastName = "Norman",    
                    EnrollmentDate = DateTime.Parse("2013-09-01") },
                new Student { FirstMidName = "Nino",     LastName = "Olivetto",  
                    EnrollmentDate = DateTime.Parse("2005-08-11") }
            };

            students.ForEach(s => context.Students.AddOrUpdate(p => p.LastName, s));
            context.SaveChanges();


            var courses = new List<Course>
            {
                new Course {CourseID = 1050, Title = "Chemistry",      Credits = 3, },
                new Course {CourseID = 4022, Title = "Microeconomics", Credits = 3, },
                new Course {CourseID = 4041, Title = "Macroeconomics", Credits = 3, },
                new Course {CourseID = 1045, Title = "Calculus",       Credits = 4, },
                new Course {CourseID = 3141, Title = "Trigonometry",   Credits = 4, },
                new Course {CourseID = 2021, Title = "Composition",    Credits = 3, },
                new Course {CourseID = 2042, Title = "Literature",     Credits = 4, }

            };
            courses.ForEach(s => context.Courses.AddOrUpdate(p => p.Title, s));
            context.SaveChanges();


            var enrollments = new List<Enrollment>
            {
                new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Alexander").StudentID, 
                    CourseID = courses.Single(c => c.Title == "Chemistry" ).CourseID, 
                    Grade = Grade.A 
                },
                 new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Alexander").StudentID,
                    CourseID = courses.Single(c => c.Title == "Microeconomics" ).CourseID, 
                    Grade = Grade.C 
                 },                            
                 new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Alexander").StudentID,
                    CourseID = courses.Single(c => c.Title == "Macroeconomics" ).CourseID, 
                    Grade = Grade.B
                 },
                 new Enrollment { 
                     StudentID = students.Single(s => s.LastName == "Alonso").StudentID,
                    CourseID = courses.Single(c => c.Title == "Calculus" ).CourseID, 
                    Grade = Grade.B 
                 },
                 new Enrollment { 
                     StudentID = students.Single(s => s.LastName == "Alonso").StudentID,
                    CourseID = courses.Single(c => c.Title == "Trigonometry" ).CourseID, 
                    Grade = Grade.B 
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Alonso").StudentID,
                    CourseID = courses.Single(c => c.Title == "Composition" ).CourseID, 
                    Grade = Grade.B 
                 },
                 new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Anand").StudentID,
                    CourseID = courses.Single(c => c.Title == "Chemistry" ).CourseID
                 },
                 new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Anand").StudentID,
                    CourseID = courses.Single(c => c.Title == "Microeconomics").CourseID,
                    Grade = Grade.B         
                 },
                new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Barzdukas").StudentID,
                    CourseID = courses.Single(c => c.Title == "Chemistry").CourseID,
                    Grade = Grade.B         
                 },
                 new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Li").StudentID,
                    CourseID = courses.Single(c => c.Title == "Composition").CourseID,
                    Grade = Grade.B         
                 },
                 new Enrollment { 
                    StudentID = students.Single(s => s.LastName == "Justice").StudentID,
                    CourseID = courses.Single(c => c.Title == "Literature").CourseID,
                    Grade = Grade.B         
                 }
            };


            foreach (Enrollment e in enrollments)
            {
                var enrollmentInDataBase = context.Enrollments.Where(
                   s =>
                        s.Student.StudentID == e.StudentID &&
                        s.Course.CourseID == e.CourseID).SingleOrDefault();

                if (enrollmentInDataBase == null)
                {
                    context.Enrollments.Add(e);
                }
            }
            context.SaveChanges();

        }
    }
}

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Seed 方法，在Code First Migrations 建立database以及每一次从上次的migrations 进行update database的时候执行。Seed方法的目的是可让你在application 读取database数据以前向tables中insert data.

Seed方法中添加的数据大部分是测试用的，或者是一些发布到正式环境也必须有的数据，例如部门信息等，这样咱们在开发的时候就不用每一次都手动的进行添加数据。

1，更新Seed方法，这样程式运行的时候就会加载这些测试数据

Seed方法把database context对象做为输入参数，而后添加新的实体到database中。对于每个实体类型来讲，code首先建立了实体的集合（list），而后把他们添加到对应的DbSet属性中，而后用SaveChange()方法保存到database.

AddOrUpdate方法执行了一个插入更新的动做。每一次Mirgraiton的时候Seed方法都会执行，它会把开发测试过程当中的更新重写到database中。

context.Students.AddOrUpdate(p => p.LastName, s)

AddOrUpate中的第一个参数，指定根据这个参数的属性去检查实体数据是否存在。在测试的Student data中，咱们用LastName,由于在List的列表中，LastName是惟一的。

若是咱们添加一条LastName重复名称的student.当你进行database migrations的时候就会报出下面的错误：

Sequence contains more than one element

   foreach (Enrollment e in enrollments)
            {
                var enrollmentInDataBase = context.Enrollments.Where(
                   s =>
                        s.Student.StudentID == e.StudentID &&
                        s.Course.CourseID == e.CourseID).SingleOrDefault();

                if (enrollmentInDataBase == null)
                {
                    context.Enrollments.Add(e);
                }
            }
            context.SaveChanges();

Seed方法中添加Enrollment Entities的时候，并无用到AddOrUpdate方法。

而是用了Add，这个方法会检查enrollment 实体数据是否存在，不存在的话加入一条新的数据，若是存在不会对其进行更新。Foreach循环遍历 Enrollment中的每个实体，在你第一次update database的时候，这些实体就会被添加到database中。

2.Ctrl+Shift+B重建解决方案：

5.3 Create and Execute the First Migration建立并执行迁移

1，Package Manager Console中输入命令建立最开始的迁移，并更新

1.  PM>add-migration InitialCreate

2.  PM>update-database

add-migration 命令添加了Migrations文件夹，而且包含迁移类文件，迁移类生成了database. InitialCreate是本身定义的参数名字。

迁移类中的Up方法，建立了和Model Class中实体集合(entity sets)对应的database tables. Down方法是删除这些实体。Migrations调用Up方法去执行data model 中的改变。当你Update-database的时候，Migrations调用了Down方法。

update-database 先调用Up方法建立数据库，而后调用Seed方法把数据填充到数据库中。

完成以上，咱们便在App_Data中建立了一个.mdf后缀的SQL Server 数据库文件。.mdf文件的名字是咱们在webconfig的链接字符串中定义的。

咱们看到资料库和.mdf文件：

6、Creating a Student Controller and Views

总结：

咱们建立了一个简单的application。接下来，咱们会学习如何执行CRUD(create,read,update,delete)。

C#基础：