c# - 仅将 IDbInterceptor 挂接到 EntityFramework DbContext 一次

Question

IDbCommandInterceptor接口(interface)没有很好的记录。而且我只找到了一些关于它的稀缺教程:

• 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 SO 问题:

• Entity Framework 6 - Timing queries
• Getting DbContext from implementation of IDbCommandInterceptor

---

这些是我发现的关于 Hook 的建议:

1 - 静态 DbInterception 类:

DbInterception.Add(new MyCommandInterceptor());

2 - 在 DbConfiguration 类中执行上述建议

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>

---

虽然我不知道如何将 DbConfiguration 类 Hook 到 DbContext，也不知道在 config 方法的 type 部分放什么。 Another example I found似乎建议您编写记录器的 namespace :

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

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

type="DataLayer.Logging.MyCommandInterceptor, DataLayer"

当我直接调用静态DbInterception 类时，它会在每次调用时添加另一个拦截器。所以我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/预期的方法是什么？

Answer 1

我发现我的 DbContext 类只需要具有 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());
    }
}