Hooking IDbInterceptor to EntityFramework DbContext only once

c# entity-framework entity-framework-6 interceptor logging

Question

The IDbCommandInterceptor interface is not very well documented. And I've only found a few scarce tutorials on it:

And a few SO questions:


These are the suggestions on hooking I've found:

1 - The static DbInterception class:

DbInterception.Add(new MyCommandInterceptor());

2 - Doing the above suggestion in a DbConfiguration class

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

3 - Using the config file:

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

Although I couldn't figure out how to hook the DbConfiguration class to the DbContext, and neither what to put in the type part of the config method. Another example I found seemed to suggest that you write the namespace of a logger:

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

I noted that DataBaseLogger implements IDisposable, IDbConfigurationInterceptor and
IDbInterceptor. IDbCommandInterceptor also implements IDbInterceptor, so I tried (without success) to format it like this:

type="DataLayer.Logging.MyCommandInterceptor, DataLayer"

And when I called the static DbInterception class directly, it added another interceptor every call. So my quick and dirty solution was to utilize static constructors:

//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() { }
    }
}

But what are the proper/intended ways to do it?

1
8
5/23/2017 12:00:08 PM

Accepted Answer

I figured out that my DbContext class just needed to have the DbConfigurationType attribute, to attach a configuration at runtime:

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

public class MyDBConfiguration : DbConfiguration {
    public MyDBConfiguration() {
        this.AddInterceptor(new MyCommandInterceptor());
    }
}
8
2/23/2017 4:35:59 PM

Popular Answer

The docs suggests that you can just put it in 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());
}

The important part is that it only get's called once.



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