Entity Framework 4.1 The model backing the context

Question

I am working on a project which uses Entity Framework 4.1 for persisting our various objects to the database (code first).

I am testing in Visual Studio with a local SQL Express DB, and our Jenkins server deploys committed code to a testing server. When this happens I temporarily change my local connection string to point to the testing DB server and run a unit test to re-create the test database so that it matches our latest entities, etc.

I've recently noticed our testing server is giving this error:

The model backing the 'EntityFrameworkUnitOfWork' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data.

This is usually an indication that our code has changed and I need to run the unit test to re-create the database. Except I just did that! I don't believe there is anything wrong with our deployment process - the DLLs on the test server seem to be the same versions as in my local environment. Are there any other settings or environment factors that can cause this error about the model having changed since the database was created?

I'm new here - thanks for any help!

Answer 1

Are the two servers running your application running different operating systems (or service packs?) It appears the SHA256CryptoService used can throw a PlatformNotSupportedException which causes it to fallback to another method.

http://msdn.microsoft.com/en-us/library/system.security.cryptography.sha256cryptoserviceprovider.sha256cryptoserviceprovider.aspx

// System.Data.Entity.Internal.CodeFirstCachedMetadataWorkspace
private static SHA256 GetSha256HashAlgorithm()
{
  SHA256 result;
  try
  {
    result = new SHA256CryptoServiceProvider();
  }
  catch (PlatformNotSupportedException)
  {
    result = new SHA256Managed();
  }
  return result;
}

You may be able to test this by using reflection to invoke the following 2 (internal/private) methods on each server.

MetaDataWorkspace.ToMetadataWorkspace(DbDatabaseMapping, Action<string>)
CodeFirstCachedMetadataWorkspace.ComputeSha256Hash(string xml);