WCF DataService throws ConnectionString exception on insert

Question

My WCF Data Service works great when I fetch data from it. When I try to insert new data, I get the following exception:

The ConnectionString property has not been initialized

The only thing I modified is to use my partial class that tells to use the connection string name:

public MyExtEntities(string connectionString) : base(connectionString) { ... } : base(connectionString) { ... }

And I overrode the CreateDataSource, so always have the proper context:

protected override MyExtEntities CreateDataSource()
{
    MyExtEntities entities = null;
    try
    {
        entities = new MyExtEntities ("name=MyExtEntities");
        ...
        return entities;

And you can believe, the config file contains that key:

add name="MyExtEntities " connectionString="metadata=res://*...

The stack shows that the core system is running, nothing from my methods:

System.Data.EntityClient.EntityConnection.Open()
at: System.Data.Objects.ObjectContext.EnsureConnection()
at: System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)

at: System.Data.Entity.Internal.InternalContext.SaveChanges()
at: System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
at: System.Data.Entity.DbContext.SaveChanges()
at: lambda_method(Closure , Object )
at: System.Data.Services.Providers.DbContextHelper.<>c_DisplayClass4.b_0()
at: System.Data.Services.Providers.ObjectContextServiceProvider.SaveContextChanges()
at: System.Data.Services.Providers.ObjectContextServiceProvider.SaveChanges()
at: System.Data.Services.Providers.EntityFrameworkDataServiceProvider.SaveChanges()
at: System.Data.Services.DataService1.HandleNonBatchRequest(RequestDescription description) <br> at: System.Data.Services.DataService1.HandleRequest()

I already added this to OnStartProcessingRequest:

protected override void OnStartProcessingRequest(ProcessRequestArgs args)
{
    if (this.CurrentDataSource == null)
        this.CreateDataSource();
    base.OnStartProcessingRequest(args);
}

It's really strange that the fetching works and it uses the same connection... What should I check?

Answer 1

Well, to fix the unexplainable, here is a way.
For an unknown reason, when the CreateDataSource method creates a new DbContext instance, it doesn't always have a Connection String. To prevent this from happenning, I created a DbContext instance along with the DataService class to ensure that I have a proper instance:

public class InformationDataService : DataService<InformationEntities>
  {
    private InformationEntities context = new InformationEntities("name=InformationEntities");

After that I modified the overriden CreateDataSource to always return the initially created (and hopefully properly working) DbContext:

protected override InformationEntities CreateDataSource()
    {
      if (context == null)
                return new InformationEntities("name=InformationEntities");
      return context;
    }

After these modifications, the error is gone.