开始本篇文章之前,先说一下Entity Framework 6 Alpha1在NuGet中已可用,原文链接http://blogs./b/adonet/archive/2012/10/30/ef6-alpha-1-available-on-nuget.aspx 俗话说:“工欲善其事必先利其器”,在深入讲解Entity Framework之前,先准备一下开发工具以及前期的配置。 一、开发工具开发工具基本略过,这里说一下,我使用的是Visual Studio 2012,Entity Framework版本为4.3.1,获取这个版本的办法:在Package Manager Console中输入Install-Package EntityFramework -Version 4.3.1。至于数据库,主要是LocalDb。 二、连接数据库当使用NuGet安装完Entity Framework后,在配置文件中会自动加入entityFramework节,里面有defaultConnectionFactory元素,如下: 1: <?xml version="1.0" encoding="utf-8"?> 2: <configuration> 3: <configSections> 4: <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --> 5: <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=4.3.1.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /> 6: </configSections> 7: <entityFramework> 8: <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework"> 9: <parameters> 10: <parameter value="Data Source=(localdb)\v11.0; Integrated Security=True; MultipleActiveResultSets=True" /> 11: </parameters> 12: </defaultConnectionFactory> 13: </entityFramework> 14: </configuration> 在没有提供具体数据库连接的情况下,EF默认使用这一配置。如上面代码中,默认会连接到LocalDb,数据库的名称为上下文完全限定名(命名空间+类名)。以前经常提到默认连接到.\SQLEXPRESS,因为安装的版本不同。 EF中提供了两个连接工厂:SqlConnectionFactory和SqlCeConnectionFactory。使用方式分别如下: 1: Database.DefaultConnectionFactory = new SqlConnectionFactory("Data Source=.;Database=Test;UId=sa;Pwd=sasa;MultipleActiveResultSets=True"); 或 1: Database.DefaultConnectionFactory = new SqlConnectionFactory("Data Source=.;Database=Test;User=sa;Password=sasa;MultipleActiveResultSets=True"); 和 1: Database.DefaultConnectionFactory = new SqlCeConnectionFactory("System.Data.SqlServerCe.4.0"); 在配置文件和代码中同时有DefaultConnectionFactory的情况下,代码中的优先。 下面,写一个简单的控制台程序。代码如下: 1: namespace ConnectDatabase 2: {
3: class Program 4: {
5: static void Main(string[] args) 6: {
7: using (TestContext ctx = new TestContext()) 8: {
9: var blog = new Blog() 10: {
11: Name = "EF" 12: };
13: blog.Posts.Add(new Post() 14: {
15: Title = "连接数据库", 16: Content = "这是连接数据库的测试", 17: Creationdate = DateTime.Now,
18: Blog = blog
19: });
20: ctx.Blogs.Add(blog);
21: ctx.SaveChanges();
22:
23: foreach (var item in ctx.Blogs) 24: {
25: Console.WriteLine(item.Name);
26: }
27: }
28: }
29: }
30:
31: public class TestContext : DbContext 32: {
33: protected override void OnModelCreating(DbModelBuilder modelBuilder) 34: {
35: base.OnModelCreating(modelBuilder); 36: }
37:
38: public DbSet<Blog> Blogs { get; set; } 39: public DbSet<Post> Posts { get; set; } 40: }
41:
42: public class Blog 43: {
44: public Blog() 45: {
46: Posts = new List<Post>(); 47: }
48:
49: public int Id { get; set; } 50: public string Name { get; set; } 51: public virtual List<Post> Posts { get; set; } 52: }
53:
54: public class Post 55: {
56: public int Id { get; set; } 57: public string Title { get; set; } 58: public string Content { get; set; } 59: public DateTime Creationdate { get; set; } 60: public virtual Blog Blog { get; set; } 61: }
62: }
使用默认连接配置,生成的数据库名称为:ConnectDatabase.TestContext,如下图所示: 重写上面配置有以下方法: 1.在配置文件中添加connectionStrings,name和上下文类名一致。 1: <connectionStrings> 2: <add name="TestContext1" connectionString="Data Source=(localdb)\v11.0;Database=Test;Integrated Security=True;MultipleActiveResultSets=True" providerName="System.Data.SqlClient"/> 3: </connectionStrings> 2.同1,但是name和上下文类名不一致。这就需要修改TextContext代码,如下: 1: public TestContext() : this("TestContext1") { } 2:
3: public TestContext(string nameOrConnectionString) 4: : base(nameOrConnectionString) 5: {
6:
7: }
或 1: public TestContext() 2: : base("name=TestContext1") 3: {
4:
5: }
或 1: public TestContext():base("TestContext1"){} 下面给出连接具体数据库的配置: 1.连接Sql Server数据库 1: <connectionStrings> 2: <add name="TestContext" connectionString="Data Source=.;Database=Test;User=sa;Password=sasa;MultipleActiveResultSets=True" providerName="System.Data.SqlClient"/> 3: </connectionStrings> 2.连接Sql Server Compact 4.0 1: <connectionStrings> 2: <add name="TestContext" connectionString="Data Source=|DataDirectory|\Test.sdf" providerName="System.Data.SqlServerCe.4.0"/> 3: </connectionStrings> 3.连接MySql 5.5 连接MySql数据库需要安装mysql提供程序mysql-connector-net-6.6.4,本文最后提供这些工具的下载地址。 1: <connectionStrings> 2: <add name="TestContext" 3: connectionString="User Id=root;server=localhost;password=sasa;database=test1" 4: providerName="MySql.Data.MySqlClient" /> 5: </connectionStrings> 三、数据库初始化1.关闭初始化 1: Database.SetInitializer<TestContext>(null); 2.CreateDatabaseIfNotExists 这是Entity Framework的默认初始化策略,没有必要设置它,如果真的需要设置,如下: 1: Database.SetInitializer(new CreateDatabaseIfNotExists<TestContext>()); 3.DropCreateDatabaseWhenModelChanges 如果模型发生了改变,则删除并重建数据库。 1: Database.SetInitializer(new DropCreateDatabaseWhenModelChanges<TestContext>()); 4.DropCreateDatabaseAlways 无论模型和数据库匹配与否,都删除并重建数据库。 1: Database.SetInitializer(new DropCreateDatabaseAlways<TestContext>()); 5.Database.Initialize可以强制初始化,即使在当前AppDomain中已经发生了。下面我写个单元测试程序,来演示这一点: 1: [TestClass]
2: public class UnitTest1 3: {
4: [TestMethod]
5: public void TestForceInitialize() 6: {
7: //说明一点:我Demo中的TestContext和Microsoft.VisualStudio.TestTools.UnitTesting.TestContext冲突了,所以写成了ConnectDatabase.TestContext 8: //Arrage 9: Database.SetInitializer(new DropCreateDatabaseAlways<ConnectDatabase.TestContext>()); 10: //Act 11: using (ConnectDatabase.TestContext ctx = new ConnectDatabase.TestContext()) 12: {
13: ctx.Database.Initialize(force: true); 14: ctx.Blogs.Add(new ConnectDatabase.Blog() 15: {
16: Name = "强制初始化1" 17: });
18: ctx.SaveChanges();
19: }
20: using (ConnectDatabase.TestContext ctx = new ConnectDatabase.TestContext()) 21: {
22: ctx.Database.Initialize(force: true); 23: ctx.Blogs.Add(new ConnectDatabase.Blog() 24: {
25: Name = "强制初始化2" 26: });
27: ctx.SaveChanges();
28: }
29: ConnectDatabase.Blog blog = null; 30: using (ConnectDatabase.TestContext ctx = new ConnectDatabase.TestContext()) 31: {
32: blog = ctx.Blogs.FirstOrDefault();
33: }
34:
35: //Assert 36: Assert.IsNotNull(blog);
37: Assert.AreEqual("强制初始化2", blog.Name); 38:
39: }
40: }
测试结果: 因为设置的初始化策略为DropCreateDatabaseAlways,每一次调用Database.Initialize,参数为true,都会重新删除并创建数据库。 四、Seed数据创建数据库时初始化一些数据,首先自定义初始化策略,重写Seed方法,代码如下: 1: public class DropCreateDatabaseWithSeedData : DropCreateDatabaseAlways<TestContext> 2: {
3: protected override void Seed(TestContext context) 4: {
5: context.Blogs.Add(new Blog() 6: {
7: Name = "种子数据1" 8: });
9: context.Blogs.Add(new Blog() 10: {
11: Name = "种子数据2" 12: });
13: //注意没有调用context.SaveChanges(),base.Seed(context)会调用 14: base.Seed(context); 15: }
16: }
下面是测试程序: 1: [TestMethod]
2: public void SeedData() 3: {
4: Database.SetInitializer(new DropCreateDatabaseWithSeedData()); 5: List<ConnectDatabase.Blog> blogList = null; 6: using (ConnectDatabase.TestContext ctx = new ConnectDatabase.TestContext()) 7: {
8: blogList = ctx.Blogs.OrderBy(t => t.Id).ToList();
9: }
10: Assert.AreEqual(2, blogList.Count);
11: Assert.AreEqual("种子数据1", blogList[0].Name); 12: Assert.AreEqual("种子数据2", blogList[1].Name); 13: }
测试结果: 五、创建索引在Seed方法中,使用ExecuteSqlCommand创建索引,代码如下: 1: protected override void Seed(TestContext context) 2: {
3: context.Database.ExecuteSqlCommand("CREATE INDEX IX_Test_Name ON Blogs (Name)"); 4: context.Blogs.Add(new Blog() 5: {
6: Name = "种子数据1" 7: });
8: context.Blogs.Add(new Blog() 9: {
10: Name = "种子数据2" 11: });
12: //注意没有调用context.SaveChanges(),base.Seed(context)会调用 13: base.Seed(context); 14: }
六、结束语mysql相关工具下载地址: 2.mysql-connector-net-6.6.4.msi 3.mysql-workbench-gpl-5.2.44-win32.msi 本篇中主要讲了Entity Framework连接数据库、初始化的一些知识,跟题目”工欲善其事必先利其器“有点不符,但仔细想想也相差不了多远,解决了最基本的,后面的才能更顺利。 点击查看《Entity Framework实例详解》系列的其他文章。 如果遇到问题,可以访问Entity Framework社区,网址是www. |
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