Problems in WCF scenario

Hello,

Our company evaluates LightSpeed (most current version - 5), we are mostly interested in using it in distributed scenario where WPF client applications connect to WCF host. Basing on the user guide and provided samples I managed to prepare working solution which uses WCF. However I encountered few problems for which I cannot find answers.

I replicated my problems in very simple visual studio solution and the database which contains only two tables: “Customers “ and “Orders”; both tables have integer “ID” as primary key, table “Orders” has foreign key “CustomerID “ with ID of customer from table Customers.

Let say there is a customer with ID nr 1 and name “Andrew”, for this customer I want to create new Order. For non WCF scenario I do it in following way:

LightSpeedContext<ModelUnitOfWork> context = new LightSpeedContext<ModelUnitOfWork>("Development");

using (var unitOfWork = context.CreateUnitOfWork())
{
try
{
Order newOrder = new Order();

newOrder.Customer = unitOfWork.Customers.FirstOrDefault(c => c.Name == "Andrew");
newOrder.Name = "Desk";
newOrder.Value = 100;
unitOfWork.Add(newOrder);                                
unitOfWork.SaveChanges();
}
catch (Exception ex)
{
string message = ex.Message;
}             
}

Important is line:

newOrder.Customer = unitOfWork.Customers.FirstOrDefault(c => c.Name == "Andrew");

When I assign reference to Customer then implicitly CustomerId integer value foreign key is set, this works ok - after save changes I have new order in my database. However when I want to do the same operation for WCF application:

public static LightSpeedContext<UnitOfWorkDistributedModel> _contextConfig;

static void Main(string[] args)
{
    _contextConfig = new LightSpeedContext<UnitOfWorkDistributedModel>("default")
    {
        UnitOfWorkFactory = new DistributedUnitOfWorkFactory<UnitOfWorkDistributedModel>()
    };

    using (var unitOfWork = _contextConfig.CreateUnitOfWork())
    {
            try
        {
            Order newOrder = new Order();

            newOrder.Customer = unitOfWork.Customers.FirstOrDefault(c => c.Name == "Andrew");
            newOrder.Name = "Desk";
            newOrder.Value = 100;
            unitOfWork.Add(newOrder);

            unitOfWork.SaveChanges();
        }
        catch (Exception ex)
        {
            string message = ex.Message;
        }             
    }

}

I always get exception “Failed to commit to server”, and this is probably because in this scenario foreign key CustomerId is not being set (it has 0 value while it should have 1), however I can see in a debugger that newOrder.Customer reference is not null – it has proper values for that customer. Neverthelees CustomerID field is not set. After calling UnitOfWork.SaveChanges exception is thrown. Interestingly when I set CustomerID foreign key manually to 1 save changes commits properly.

Questions:

1. Why in distributed scenario foreign key integer (CustomerID in this example) value is not set automatically after setting backreference value (Customer in this example)? In local mode it works ok.
2. User Vincente in thread: http://www.mindscapehq.com/forums/thread/4374 asked about more robust way of logging problems in DistributedUnitOfWork in WCF scneraio. However I cannot find any improvements since that time. I mostly get "Failed to commit changes to the server" exception which is really too little informative in production environment. I tried hooking the GeneralFailureOccurred event but there are no many more valuable information in its exception message. What can I do to get more information when save changes throws exception?
3. Validation in distribution scenario – I set Validate Unique on entity field. In non-distributed scenario IsValid value is false when the field value already exists in table. However in distributed scenario validation does not work. I add entity with value that I know that already exists in database – validation passes (IsValid == true) but on SaveChanges I get exception. How can I validate uniqueness in distributed scenario?

I can send you VisualStudio2010 solution and backup of SQLServer database if it can help (should I attach it in thread or send it to you directly by an email?) .

Regards.

Can someone help me?

Regards.

re #1: This sounds like incorrect behaviour on the face of it, would you be able to send through the repro you mentioned and we can have a more detailed look into what is going on here.

re #2: The message you are referring to is raised when the SaveChanges call failed (so either a ValidationException or a LightSpeedException occurred at the server). We dont surface any more specific details but this should be treated as a failure to persist due to issues at the database (e.g. FK violation or Unique violation or network failure). Based on your other comments this may occur if you have a server side validation like a unique check in which case you should do an upfront query to check for this problem before you call SaveChanges().

re #3: Server side validations such as unique checks have to be run at the server so they are ignored at the client level. In general you should validate these yourself before calling SaveChanges because as mentioned above they will be lumped in with other database level failures when reporting success/failure so you wont be able to determine specifically why it failed.

Thanks!
Jeremy