"Metadata information not found" while using EF4's POCO Template?

Question

I just installed the POCO Template for EF4. I have a single entity in my model, AnnouncementText, and the T4 files seem to be properly generated. Attempting to access this new entity is throwing the following error when I access the auto-generated property MyObjectContext.AnnouncementTexts:

InvalidOperationException: Mapping and metadata information could not be found for EntityType 'MyNamespace.AnnouncementText'.

The properties on the AnnouncementText POCO seem to match up with the columns in the database, and I haven't changed any of the auto-generated code.

The stack trace is:

   at System.Data.Objects.ObjectContext.GetTypeUsage(Type entityCLRType)
   at System.Data.Objects.ObjectContext.GetEntitySetForNameAndType(String entitySetName, Type entityCLRType, String exceptionParameterName)
   at System.Data.Objects.ObjectContext.CreateObjectSet[TEntity](String entitySetName)
   at MyNamespace.MyObjectContext.get_AnnouncementTexts() in C:\<snip>\MyObjectContext.Context.cs:line 65
   at MyNamespace.Class1.Main() in C:\<snip>\Class1.cs:line 14

If I delete the .tt files from the solution and enable code generation on the model, I am able to access the property without issue.

Here's my code, in case that might help:

using (var context = new MyObjectContext())
   foreach (var at in context.AnnouncementTexts)
      Console.WriteLine(at.Title);

Any ideas on what might be wrong?

Solution 1

I recently ran into this same error again while moving my EDMX file to a new location in the solution. Apparently, there are a couple of different namespaces when dealing with EDMX files. There is the namespace you enter via the wizard when creating the initial EDMX file (N1), another that appears in the SSDL which looks something like this (N2):

<Schema Namespace="..." ..

Then there's the namespace of the generated code which may (optionally) be specified in the designer (N3), and finally there are the hidden namespaces of the resources that are compiled in to your final assembly (N4).

From what I can tell, namespace N2 is only really relevant inside the SSDL. I believe this namespace starts off as N1 - the one you initially enter in the wizard.

Similarly, namespace N3 is only relevant in the way C# namespaces usually are.

Here's the problematic part. Category N4 namespaces are a function of the directory in which your EDMX resides (relative to your project directory). You might think, So what? It turns out those namespaces are also referenced in your App.config file! Specifically, look for a part like this:

connectionString="metadata=res://*/Database.Master.csdl|...

That portion reading "Database.Master.csdl" is the name of your CSDL resource. If those resource names get out of sync, you'll receive an error like the one above, or perhaps:

The specified default EntityContainer name '[name]' could not be found in the mapping and metadata information.

The simple solution is to alter your App.config to specify the correct resource name for each part of your EF mapping (CSDL, SSDL, and MSL). If you're not sure exactly what those names are, check out your compiled assembly's resources in ILSpy or dotPeek.

Solution 2

If you copy an EDMX file to another project, the Build Action (in the Properties pane) will revert to the default value of "None" in the target project, which can cause the "EntityContainer name . . . could not be found" error, which is because no resources are being generated. (If this is the case, when you open the DLL containing the model in Reflector there will be no resources.) Setting the Build Action to "EntityDeploy" and rebuilding the solution will correct this.

Solution 3

Not sure about this one... it does seem a little wierd, so this is a long shot.

But sometime the occasional ObjectContext.MetadataWorkspace.LoadFromAssembly() call helps.

And even if it doesn't there is a second overload that provides trace style output.

i.e.

Assembly assembly = typeof(AnnouncementText).Assembly;
context.MetadataWorkspace.LoadFromAssembly(
    assembly, 
    (message) => Console.WriteLine(message)
);
foreach(var at in context.AnnouncementTexts)
   ...

And see what messages you get (if any).

Hope this helps

Alex

Solution 4

On the Solution Explorer, right click on the Entity Data Model file (.edmx) and click 'Open with'. A dialog box will open up to choose a program for you to open the file. Select or Double click on 'XML (text) Editor'.

Now you re looking at the XML version of the EDM file where you can easily edit the 'EntityContainer' name.

If you have changed the connectionstring on the webconfig file, make sure the 'DefaultContainerName' is the name on section 'EntityContainer' in that XML file.

Usually when you update the defaultContainerName in *.Designer.cs file, it doesn't update the XML file. So you have do it manually.

Solution 5

I had a similar issue when integrating various projects.
The issue was that I had more than one edmx since I had many projects.

The connection string was the same, but the namespace was different.

To solve this, choose one of the connections to use and change the others.
Be aware that you will need to make the change in the designer.cs and also in the xml file.

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Comments

[Athabaska Dick]

Do you have multiple edmx files in your project?

[ladenedge]

I'm afraid I just added a single edmx to test the functionality iirc, though since posting this question I've moved to VS 2010 RC1. As the POCO Template has only been available for a few days, I haven't yet had a chance to see if my problem has persisted.

[ladenedge]

Well, that doesn't seem to do (or print) anything in this case. I also tried removing the POCO stuff and using the default entity generation with your example code, and I'm afraid I didn't see any output in that case either. Thanks for the attempt! Shots in the dark are more than welcome, heh.

[kdawg]

Awesome, exactly what I was looking for. I had moved my edmx file to within a new folder, and indeed, the missing namespace information in the metadata connectionstring for EF was the culprit. Thanks!

[BlueRaja - Danny Pflughoeft]

I was getting the error "Unable to load specified metadata resource" after refactoring my database code from its own folder to its own class-library. This answer explained and fixed the problem. Thanks!