Add an interceptor to an existing DbContext instance

[Giorgi]

I know that interceptors can be added when creating the model using DbContextOptionsBuilder.AddInterceptors method but is there a way to add an interceptor instance on an existing DbContext instance?

This can be useful for third party library developers which want to add interception capability to the existing DbContext instance.

[ajcvickers]

Putting this on the backlog as something that would be useful. However, traditional events may be more appropriate--see #626.

[Giorgi]

So this means that there is no way to do it in the 3.1 version right ?

[ajcvickers]

@Giorgi Correct.

[Giorgi]

There is also no way to get the command text and parameters from IQueryable<> neither.

[ajcvickers]

@Giorgi See #19358

[Giorgi]

Yes, looks like I will have to wait until EF Core 5

[jamiewinder]

Since this is quite an old issue, is there a way to do this currently? In my case, I'm hoping to be able to attach a connection interceptor to an existing DbContext (or through a IDbContextFactory if more appropriate) with an interceptor that performs tenancy isolation. Basically so I can implement a DbContext CreateTenantContext(Guid tenantId) factory method. As far as I can tell, my only option at the moment is to create a DbContext, force the connection to open (so it stays open), and then run a command on it.

[ajcvickers]

@jamiewinder With a context factory, you control creating the instance of the context, so you can add whatever interceptors you want there. There isn't a way to add interceptors after the context has been initialized; this issue is tracking that.

[jamiewinder]

@ajcvickers Thanks. Just to make sure I'm understanding correctly, I think I'm correct in saying that currently I can only control which interceptors are added when the factory is created rather than when I ask if for a context to be created? i.e. I can't do anything like this:

private readonly IDbContextFactory<MyContext> _contextFactory;

public MyContext CreateTenantContext(Guid tenantId)
{
   var setTenancyInterceptor = new SetTenancyInterceptor(tenantId);
   return _contextFactory.CreateDbContextWithInterceptors(setTenancyInterceptor);
}

(obviously CreateDbContextWithInterceptors isn't a thing, just an example)

[ajcvickers]

You can do whatever you want in your implementation of IDbContextFactory.

[jamiewinder]

It seems I grossly overestimated what was involved in creating a IDbContextFactory! That's perfect, thanks for the pointers!