entity-framework - 实体框架资源和建议

Question

最近几周我一直在学习实体框架，接触过 ADO.Net 和一些 LINQ 语法。在您真正开始开发这些东西之前，我基本上找到了很多设置和接线要做。我在 Code First 方法中特别难过，也曾在 Julie Larnam 的热情博客中度过了一段时间。任何关于实体框架的书籍、文章或博客的建议，以加快我的学习和更深入的理解，我们将不胜感激。

谢谢阿拉西

Answer 1

初始化

第一步，设置模型

public class Person
{
    public Int32 Id { get; set; }
    public String Name { get; set; }
    public String Email { get; set; }

    // one-to-many relationship to Pet (EF picks up on this automatically)
    public ICollection<Pet> Pets { get; set; }
}
public class Pet
{
    public Int32 Id { get; set; }
    public String Name { get; set; }
    public String Breed { get; set; }

    // foreign key back to person (EF picks up on this automatically)
    public Person Owner { get; set; }
}

第二步，使用模型创建上下文

public MyContext : DbContext
{
    public DbSet<Person> Persons { get; set; }
    public DbSet<Pet> Pets { get; set; }


}

第三步，创建connectionString

提示：连接字符串的名称应与您的上下文匹配。

<connectionStrings>
  <add name="MyContext"
       providerName="System.Data.SqlClient"
       connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=MyContext;IntegratedSecurity=True;" />
</connectionStrings>

跑过，匆匆处理

基本的

// automatically find the connection string matching the context name,
// as well as performs a check to see if:
// 1. The database exists
// 2. The schema is up-to-date
MyContext context = new MyContext();
context.Persons.Add(new Person {
  Name = "Brad Christie",
  Email = "bchristie@contoso.com"
});
context.SaveChanges();

中间的

您还可以使用 更改数据的生成方式Initializers。例如，如果您想使用信息预先填充数据库，您可以执行以下操作：

public class MyContextInitializer
  // this could be `DropCreateDatabaseAlways<TContext> or any other
  // preexsting initializer:
  : DropCreateDatabaseIfModelChanges<MyContext>
  // you can also create your own explicitly if you implement the
  // following interface, but that's a bit much starting out.
  //: IDatabaseInitializer<MyContext>
{
    protected override void Seed(MyContext context)
    {
       new List<Person> {
           new Person {
               Name = "Brad Christie",
               Email = "bchristie@contoso.com",
               Pets = new HashSet<Pet> {
                   new Pet {
                       Name = "Spot",
                       Breed = "Dalmation"
                   }
               }
           }, new Person {
               Name = "Alaxi04",
               Email = "Alaxi04@contoso.com",
               Pets = new HashSet<Pet> {
                   new Pet {
                       Name = "Petey",
                       Breed = "Parrot"
                   }
               }
           }
       }.ForEach(p => context.Persons.Add(p));

       base.Seed(context);
    }
}

在实践中：

// call this somewhere early on in the application (but only once!)
Database.SetInitializer<MyContext>(new MyContextInitializer());
// This can also be configured through the `web.config`:
<entityFramework>
  <contexts>
    <context type="MyNamespace.MyContext, MyAssembly">
      <databaseInitializer type="MyNamespace.MyContextInitializer, MyAssembly" />
    </context>
  </contexts>
</entityFramework>

/* ***** */

 // then use the context as normal:
 MyContext context = new MyContext();
 var petOwners = context.Persons.AsEnumerable();