MVC5 + EF6執行個體(Code First 方式生成資料庫及初始化資料庫)
本執行個體的學習環境: VS2015 + EF 6.2.0+ .NET 4.5.2
建立工程:
1.建立一個C# MVC Web應用程式(我起名為EFTest)
2. 在“ 建立ASP.NET項目”對話框中,選擇MVC模闆。更改身份驗證,改為不進行身份驗證(N)
3. 通過NuGet包管理器安裝EF6
代碼編寫:
1.打開視圖\ Shared \ _Layout.cshtml,并進行以下更改,如下圖出顯示:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>@ViewBag.Title - University Managerr</title>
@Styles.Render("~/Content/css")
@Scripts.Render("~/bundles/modernizr")
</head>
<body>
<div class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
@Html.ActionLink("University Managerr", "Index", "Home", new { area = "" }, new { @class = "navbar-brand" })
</div>
<div class="navbar-collapse collapse">
<ul class="nav navbar-nav">
<li>@Html.ActionLink("首頁", "Index", "Home")</li>
<li>@Html.ActionLink("學生", "Index", "Student")</li>
<li>@Html.ActionLink("課程", "Index", "Course")</li>
<li>@Html.ActionLink("老師", "Index", "Instructor")</li>
<li>@Html.ActionLink("部門", "Index", "Department")</li>
<li>@Html.ActionLink("聯系方式", "Contact", "Home")</li>
<li>@Html.ActionLink("關于", "About", "Home")</li>
</ul>
</div>
</div>
</div>
<div class="container body-content">
@RenderBody()
<hr />
<footer>
<p>© @DateTime.Now.Year - University Manager</p>
</footer>
</div>
@Scripts.Render("~/bundles/jquery")
@Scripts.Render("~/bundles/bootstrap")
@RenderSection("scripts", required: false)
</body>
</html>
2. 在Views \ Home \ Index.cshtml中,使用以下代碼替換原有内容:
@{
ViewBag.Title = "Home Page";
}
<div class="jumbotron">
<h1> University Manager </h1>
</div>
<div class="row">
<div class="col-md-4">
<h2>Welcome to University Manager </h2>
<p>
Contoso University is a sample application that
demonstrates how to use Entity Framework 6 in an
ASP.NET MVC 5 web application.
</p>
</div>
<div class="col-md-4">
<h2>Build it from scratch</h2>
<p>You can build the application by following the steps in the tutorial series on the ASP.NET site.</p>
<p><a class="btn btn-default" href="http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/">See the tutorial »</a></p>
</div>
<div class="col-md-4">
<h2>Download it</h2>
<p>You can download the completed project from the Microsoft Code Gallery.</p>
<p><a class="btn btn-default" href="http://code.msdn.microsoft.com/ASPNET-MVC-Application-b01a9fe8">Download »</a></p>
</div>
</div>
3.建立資料模型
接下來,您将為Contoso University 應用程式建立實體。将從以下三個實體開始:
Student和Enrollment是一對多關系,Course和Enrollment也是一對多的關系。換句話說,學生可以注冊任何數量的課程,課程可以被任何數量的學生注冊(學生和課程是多對多關系)。
3.1在Models檔案夾中,建立一個名為Student.cs的類檔案,并使用以下代碼替換模闆代碼:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace EFTest.Models
{
public class Student
{
public int ID { get; set; }
public string LastName { get; set; }
public string FirstMidName { get; set; }
public DateTime EnrollmentDate { get; set; }
public virtual ICollection<Enrollment> Enrollments { get; set; }
}
}
3.2 在Models檔案夾中,建立Enrollment.cs并使用以下代碼替換現有代碼:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace EFTest.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; }
/*
該EnrollmentID屬性是主鍵; 該實體主鍵使用類名 加ID的命名方式,而不是直接使用ID。通常會選擇一種固定的命名方式,并在所有資料模型中使用。在這裡,可以使用任意命名方式。在後面的教程中,将看到如何使用ID,而不用classnameID,這樣更容易在資料模型中實作繼承。
該Grade屬性是一個枚舉類型。Grade類型後的問号表示該Grade屬性可以為空。空值表示未知等級或尚未配置設定。
該StudentID屬性是一個外鍵,以及相應的導航屬性Student。一個Enrollment實體與一個Student實體相關聯,是以該屬性隻能儲存一個Student實體。
該CourseID屬性也是一個外鍵,以及相應的導航屬性Course。一個Enrollment實體與一個Course實體相關聯。
*/
}
}
3.3 在Models檔案夾中,建立Course.cs,使用以下代碼替換模闆代碼:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
using System.ComponentModel.DataAnnotations.Schema;
namespace EFTest.Models
{
public class Course
{
//DatabaseGenerated屬性,DatabaseGeneratedOption.None 設定允許輸入課程主鍵,而不是讓資料庫自動生成它(不是自動增長)。
[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; }
}
}
4. 建立資料庫上下文
4.1 右鍵單擊該項目解決方案資料總管,然後單擊建立檔案夾。命名新檔案夾DAL(用于資料通路層)。在該檔案夾中建立一個名為UniversityContext.cs的類,代碼如下:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using EFTest.Models;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
namespace EFTest.DAL
{
public class UniversityContext: DbContext
{
public UniversityContext() : base("UniversityDbContext")
{
}
public DbSet<Student> Students { get; set; }
public DbSet<Enrollment> Enrollments { get; set; }
public DbSet<Course> Courses { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
//阻止表名複數形式
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
}
}
4.2 在DAL檔案夾中,建立一個名為UniversityInitializer.cs的類,代碼如下:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using EFTest.Models;
namespace EFTest.DAL
{
public class UniversityInitializer : DropCreateDatabaseIfModelChanges<UniversityContext>
{
protected override void Seed(UniversityContext context)
{
var students = new List<Student>
{
new Student{FirstMidName="zhang",LastName="san",EnrollmentDate=DateTime.Parse("2018-09-01")},
new Student{FirstMidName="zhao",LastName="si",EnrollmentDate=DateTime.Parse("2017-09-01")},
new Student{FirstMidName="wang",LastName="wu",EnrollmentDate=DateTime.Parse("2016-09-01")},
new Student{FirstMidName="sui",LastName="liu",EnrollmentDate=DateTime.Parse("2015-09-01")},
new Student{FirstMidName="zhou",LastName="qi",EnrollmentDate=DateTime.Parse("2014-09-01")},
new Student{FirstMidName="wu",LastName="ba",EnrollmentDate=DateTime.Parse("2013-09-01")},
new Student{FirstMidName="feng",LastName="jiu",EnrollmentDate=DateTime.Parse("2012-09-01")},
new Student{FirstMidName="chen",LastName="shi",EnrollmentDate=DateTime.Parse("2011-09-01")},
};
students.ForEach(s => context.Students.Add(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.Add(s));
context.SaveChanges();
var enrollments = new List<Enrollment>
{
new Enrollment{StudentID=1,CourseID=1050,Grade=Grade.A},
new Enrollment{StudentID=1,CourseID=4022,Grade=Grade.C},
new Enrollment{StudentID=1,CourseID=4041,Grade=Grade.B},
new Enrollment{StudentID=2,CourseID=1045,Grade=Grade.B},
new Enrollment{StudentID=2,CourseID=3141,Grade=Grade.F},
new Enrollment{StudentID=2,CourseID=2021,Grade=Grade.F},
new Enrollment{StudentID=3,CourseID=1050},
new Enrollment{StudentID=4,CourseID=1050,},
new Enrollment{StudentID=4,CourseID=4022,Grade=Grade.F},
new Enrollment{StudentID=5,CourseID=4041,Grade=Grade.C},
new Enrollment{StudentID=6,CourseID=1045},
new Enrollment{StudentID=7,CourseID=3141,Grade=Grade.A},
};
enrollments.ForEach(s => context.Enrollments.Add(s));
context.SaveChanges();
}
}
}
5. 修改Web.config檔案中連接配接字元串,如以下所示:
<entityFramework>
<contexts>
<context type="EFTest.DAL.UniversityContext, EFTest">
<databaseInitializer type="EFTest.DAL.UniversityInitializer, EFTest" />
</context>
</contexts>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
<parameters>
<parameter value="mssqllocaldb" />
</parameters>
</defaultConnectionFactory>
<providers>
<provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
</providers>
</entityFramework>
<connectionStrings>
<add name="UniversityDbContext" providerName="System.Data.SqlClient" connectionString="Data Source=localhost;Initial Catalog=University;Integrated Security=False;User Id=sa;Password=123456;MultipleActiveResultSets=True" />
</connectionStrings>
6. 建立Student控制器和視圖
注:如果出現以下錯誤,則表示先要編譯一下,再建View
運作檢視 Student/Index 頁面:
點選“學生”界面:
檢視資料庫
沒有點選學生界面時,不涉及通路資料庫,是以開始沒有建立資料庫。
當運作學生頁面,應用程式嘗試通路資料庫時,EF看到沒有資料庫,是以它建立了一個資料庫,然後運作Seed()方法添加測試資料。
小結:
1.使用Entity Framework能夠建立一個完整的資料庫,發現我們隻編寫了很少的代碼,因為Entity Framework有預設約定:
實體類名一般用作表名。
實體屬性名稱用于列名。
名稱ID或classnameID屬性被識别為主鍵屬性。
還有外鍵屬性,例如,StudentID用于Student導航屬性。
當然我們可以将屬性顯式地标記為外鍵屬性等