Breeze: cannot execute _executeQueryCore until metadataStore is populated

Question

I was using Breeze v1.1.2 that came with the Hot Towel template which has now been extended to form my project. I made the mistake of updating the NuGet package to the current 1.3.3 (I never learn). Anyway, all was well, and now not so much!

I followed the instructions in the release notes and other docs to change my BreezeWebApiConfig file to:

[assembly: WebActivator.PreApplicationStartMethod(
typeof(BreezeWebApiConfig), "RegisterBreezePreStart")]
namespace MyApp.App_Start {
public static class BreezeWebApiConfig {
    public static void RegisterBreezePreStart() {
      GlobalConfiguration.Configuration.Routes.MapHttpRoute(
          name: "BreezeApi",
          routeTemplate: "breeze/{controller}/{action}"
      );}}}

And the config.js file (which provides the serviceName to the EntityManager constructor) to:

var remoteServiceName = 'breeze/breeze';  // NEW version
//var remoteServiceName = 'api/breeze';  // OLD version

And my BreezeController if you're interested:

[BreezeController]
public class BreezeController : ApiController
{
    readonly EFContextProvider<MyDbContext> _contextProvider =
        new EFContextProvider<MyDbContext>();

    [HttpGet]
    public string Metadata()
    {
        return _contextProvider.Metadata();
    }

    [HttpGet]
    public IQueryable<SomeItem> SomeItems()
    {
        // Do stuff here...
    }
}

Now I get the "cannot execute _executeQueryCore until metadataStore is populated" error.

What am I missing here?

EDIT: I perhaps left out the part you needed... Above in the SomeItems() method, the stuff that actually gets done is a call to the GetMeSomeData() method in the MyDBContext class. This method makes the following call to a stored procedure to get the data.

public virtual ObjectResult<SomeItem> GetMeSomeData(string inParam)
    {
        var p = new object[] { new SqlParameter("@inParam", inParam) };
        var retVal = ((IObjectContextAdapter)this).ObjectContext.ExecuteStoreQuery<SomeItem>("exec GetData @SN", p);
        return retVal;
    }

Now given my limited understanding, the call to Metadata() is not failing, but I don't think it has any idea what the entity model is when coming back, even though somewhere along the line, it should figure that out from the entity model I do have (i.e. SomeItem)? The return string from Metadata() doesn't have any information about the entity. Is there a way to make it aware? Or am I just completely off in left field playing with the daisies?

Ward Ward · Accepted Answer · 2013-05-17T23:48:43

Hard to say based on this report. Let's see if Breeze is right.

Open the browser debugging tools and look at the network traffic. Do you see an attempt to get metadata from the server before you get that error? If so, did it succeed? Or 404? Or 500? What was the error?

I'm betting it didn't even try. If it didn't, the usual reason is that you tried some Breeze operation before your first query ... and you didn't ask for metadata explicitly either. Did you try to create an entity? That requires metadata.

The point is, you've got to track down the Breeze operation that precipitates the error. Sure everything should just work. The world should be rainbows and unicorns. When it isn't, we heave a sigh, break out the debugger, and start with the information that the error gave us.

And for the rest of you out there ... upgrading to a new Breeze version is a good thing.

Happy coding everyone.

Follow-up to your update

Breeze doesn't know how you get your data on the back-end. If the query result has a recognizable entity in it, Breeze will cache that. It's still up to you in the query callback to ensure that what you deliver to the caller is something meaningful.

You say that you're server-side metadata method doesn't have any idea what SomeItem is? Then it's not much use to the client. If it returns a null string, Breeze may treat that as "no metadata at all" in which case you should be getting the "cannot execute _executeQueryCore until metadataStore is populated" error message. Btw, did you check the network traffic to determine what your server actually returned in response to the metadata request (or if there was such a request)?

There are many ways to create Metadata on the server. The easiest is to use EF ... at least as a modeling tool at design time. What's in that MyDbContext of yours? Why isn't SomeItem in there?

You also can create metadata on the client if you don't want to generate it from the server. You do have to tell the Breeze client that you've made that choice. Much of this is explained in the documentation "Metadata Format".

I get the feeling that you're kind of winging it. You want to stray from the happy path ... and that's cool. But most of us need to learn to walk before we run.

Breeze: cannot execute _executeQueryCore until metadataStore is populated

1 Answers

Follow-up to your update