Using the same dbcontext for different models - entity-framework

Question

I have a DbContext that is empty. Mappings are created dynamically and the DbContext is used generically using Set();
The following is my generic DbContext.
/// <summary>
/// Object context
/// </summary>
public class MethodObjectContext : DbContext, IDbContext
{
private readonly IEventPublisher _eventPublisher;
public MethodObjectContext(string nameOrConnectionString, IEventPublisher eventPublisher)
: base(nameOrConnectionString)
{
_eventPublisher = eventPublisher;
}
public MethodObjectContext(DbConnection existingConnection, bool contextOwnsConnection, IEventPublisher eventPublisher)
: base(existingConnection, contextOwnsConnection)
{
_eventPublisher = eventPublisher;
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
_eventPublisher.Publish(new ModelCreating(modelBuilder));
base.OnModelCreating(modelBuilder);
}
public new IDbSet<TEntity> Set<TEntity>() where TEntity : class
{
return base.Set<TEntity>();
}
}
I am trying write a unit test that will assert that the database is out of sync if I change the mappings (from the ModelCreating event).
The following is my test code.
[TestClass]
public class MigrationTests
{
private string _connectionString = string.Empty;
private string _testDb = string.Empty;
public MigrationTests()
{
_testDb = Path.Combine("C:\\", System.Reflection.Assembly.GetExecutingAssembly().GetName().Name.Replace(".", "") + ".sdf");
if (File.Exists(_testDb))
File.Delete(_testDb);
_connectionString = string.Format("Data Source={0};Persist Security Info=False;", _testDb);
Database.DefaultConnectionFactory = new SqlCeConnectionFactory("System.Data.SqlServerCe.4.0");
}
[TestMethod]
public void ThrowsErrorForOutOfDateDatabase()
{
// The initializer will handle migrating the database.
// If ctor param is false, auto migration is off and an error will be throw saying the database is out of date.
Database.SetInitializer(new MigrationDatabaseInitializer<MethodObjectContext>(false));
// Create the initial database and do a query.
// This will create the database with the conventions of the Product1 type.
TryQueryType<Product1>("Product");
// The next query will create a new model that has conventions for the product2 type.
// It has an additional property which makes the database (created from previous query) out of date.
// An error should be thrown indicating that the database is out of sync.
ExceptionAssert.Throws<InvalidOperationException>(() => TryQueryType<Product2>("Product"));
}
private void TryQueryType<T>(string tableName) where T : class
{
using (var context = new MethodObjectContext(_connectionString, new FakeEventPublisher(x => x.ModelBuilder.Entity<T>().ToTable(tableName))))
{
var respository = new EfRepository<T>(context);
var items = respository.Table.ToList();
}
}
}
My Product1 class is a POCO object, and my Product2 class is the same object with an additional db field.
My problem is that when I new() up the MethodObjectContext the second time and do a query, the ModelCreating method isn't called, causing me to get the following error.
The entity type Product2 is not part of the model for the current context.
Product2 would be a part of the context of the ModelCreating event was being called, but it is not. Any ideas?
NOTE: I am expecting errors since we are using the same connection string (sdf) and the db being created didn't create the additional field that my second call (Product2) requires.

Answer 1

My DbCompiledModel was being cached. The following flushed the cache.
private void ClearDbCompiledModelCache()
{
var type = Type.GetType("System.Data.Entity.Internal.LazyInternalContext, EntityFramework");
var cmField = type.GetField("CachedModels",System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic);
var cachedModels = cmField.GetValue(null);
cachedModels.GetType().InvokeMember("Clear", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.InvokeMethod, null, cachedModels, null);
}