仅将IDbInterceptor挂接到EntityFramework DbContext一次

Question

该IDbCommandInterceptor接口是不是非常有据可查.我只发现了一些稀缺的教程:

• http://www.entityframeworktutorial.net/entityframework6/database-command-interception.aspx
• https://msdn.microsoft.com/en-us/data/jj556606%28v=vs.113%29.aspx
• https://entityframework.codeplex.com/wikipage?title=Interception
• https://www.tutorialspoint.com/entity_framework/entity_framework_command_interception.htm
• https://msdn.microsoft.com/en-us/data/dn469464%28v=vs.113%29.aspx

还有一些问题:

• 实体框架6 - 定时查询
• 从IDbCommandInterceptor的实现中获取DbContext

---

这些是关于挂钩的建议我发现:

1 - 静态DbInterception类:

DbInterception.Add(new MyCommandInterceptor());

2 - 在DbConfiguration课堂上做上述建议

public class MyDBConfiguration : DbConfiguration {
    public MyDBConfiguration() {
        DbInterception.Add(new MyCommandInterceptor());
    }
}

3 - 使用配置文件:

<entityFramework>
  <interceptors>
    <interceptor type="EFInterceptDemo.MyCommandInterceptor, EFInterceptDemo"/>
  </interceptors>
</entityFramework>

---

虽然我无法弄清楚如何将DbConfiguration类挂钩到DbContext,并且既没有放入typeconfig方法的部分.我发现的另一个例子似乎建议您编写记录器的命名空间:

type="System.Data.Entity.Infrastructure.Interception.DatabaseLogger, EntityFramework"

我注意到了DataBaseLogger工具IDisposable,IDbConfigurationInterceptor和
IDbInterceptor.IDbCommandInterceptor也实现了IDbInterceptor,所以我尝试(没有成功)格式化它像这样:

type="DataLayer.Logging.MyCommandInterceptor, DataLayer"

当我DbInterception直接调用静态类时,它每次调用都会添加另一个拦截器.所以我的快速而肮脏的解决方案是利用静态构造函数:

//This partial class is a seperate file from the Entity Framework auto-generated class,
//to allow dynamic connection strings
public partial class MyDbContext // : DbContext
{
    public Guid RequestGUID { get; private set; }

    public MyDbContext(string nameOrConnectionString) : base(nameOrConnectionString)
    {
        DbContextListeningInitializer.EnsureListenersAdded();

        RequestGUID = Guid.NewGuid();
        //Database.Log = m => System.Diagnostics.Debug.Write(m);
    }

    private static class DbContextListeningInitializer
    {
        static DbContextListeningInitializer() //Threadsafe
        {
            DbInterception.Add(new MyCommandInterceptor());
        }
        //When this method is called, the static ctor is called the first time only
        internal static void EnsureListenersAdded() { }
    }
}

但是,正确/有意的方法是什么？

Answer 1

我发现我的DbContext类只需要具有该DbConfigurationType属性,以便在运行时附加配置:

[DbConfigurationType(typeof(MyDBConfiguration))]
public partial class MyDbContext // : DbContext
{
    public MyDbContext(string nameOrConnectionString) : base(nameOrConnectionString)
    { }
}

public class MyDBConfiguration : DbConfiguration {
    public MyDBConfiguration() {
        this.AddInterceptor(new MyCommandInterceptor());
    }
}

Answer 2

该文档建议您可以将其放入Application_Start：

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
    DbInterception.Add(new SchoolInterceptorTransientErrors());
    DbInterception.Add(new SchoolInterceptorLogging());
}

重要的是它只被调用一次。