The retrieved entities are bound to a datagrid in which I allow new rows to be added.  My event handler is as follows:

 

private static void C1DataGrid_BeginningNewRow(object sender, DataGridBeginningNewRowEventargs e)

{

    try

    {

        BaseEntity baseEntity = e.Item as BaseEntity;

        baseEntity.EntityAspect.AddToManager();

    }

 

    catch

    {

        throw;

    }

}

 

The AddToManager call is failing with the following error "Value was either too large or too small for an unsigned byte".

 

We have other tables that have a PK column as an int that work fine.  What happens is when I say add a new row in the datagrid I am returned a number such as -100.  Eventually when I commit the entities back to the database the PK column value is resolved.

 

How do I handle this in the case where the PK on the table is a datatype such as a tinyint?

Correct, the process is as follows:  Your IIdGenerator will create a temporary ID for the new entity on the client so that the navigation relationships can be set up.  When the entity is saved, it gets assigned a permanent ID by the server and the object graph is fixed up to maintain all the relationships.

 

What you need to do is to modify your IIDGenerator so that it returns temporary IDs that fit into a tinyint.  These IDs must also not conflict with an existing ID.  Your permanent IDs could start from 0, and temporary IDs work down from 255, but this obviously gives you very little room to work with.

 

 

So I've written an IdGenerator class and I've added it to one of my assemblies that has a reference to my domain model on the client side (CMISModelSL).  First off, is this where I need to place the IdGenerator class?  I believe it is if I understand the documentation correctly.  Second, is there a way to tell if my generator is being called?  I placed breakpoints in my IdGenerator class but none of them are ever reached.  I make the following call:

 

manager.GenerateId(batchStatus, dataEntityProperty)

 

and it results in the same error from my initial post:

 

"Value was either too large or too small for an unsigned byte"

 

 

 

Also the API documentation for the method GenerateId states "If you are using a SQL Server Identity property you do not need to call GenerateId for the property".

 

In my case our "BatchStatus" database table has a PK column named "ID" that is defined as an identity key and the datatype is "tinyint".

 

Since the ID column is an identity column I'm confused why I need to call GenerateId at all?

 

When I run my code the GenerateId call fails with the error mentioned above (Value was either too large...).

 

The stacktrace is as follows:

 

 

 

 

 

 

 

 

The problem is not that DevForce assumes all identity columns are Int64, but it does assume that the target column can accept temporary values beginning with -100 and decrementing by 1.  The exception here is thrown because we are trying to convert the value -100 into a Byte, which only accepts values from 0 to 255.

 

Unfortunately, we don't have a workaround for you at the moment.  A custom IIdGenerator will not be used by DevForce for Identity columns, so this won't solve the problem.  Ideally you should be able to implement a custom IIdentityIdGenerator, or sub-class the internal DevForce StoreGeneratedIdGenerator, but that is not currently supported.   Please contact support directly to discuss options.

 

 

 

 

 

 

 

So I'm actually making some progress now.  We've removed the Identity declaration off of the column in our database table and updated our DataModel.  Interestingly enough we had to go into the model and change the "StoreGeneratedPattern" property of the column from "Identity" to "None" manually.  The update model operation didn't catch this (another bug?).  We found that this change was required as well otherwise our NumericIdGenerator was never called.  DevForce always assumed an identity column even though in the database it was no longer an identity column.

 

Anyways, now that my IdGenerator is being called I'm running into the following error when I try to commit to the database:

 

"The formatter threw an exception while trying to deserialize the message:
There was an error while trying to deserialize parameter http://ideablade.com/EntityModel:workState - http://ideablade.com/EntityModel:workState .

The InnerException message was 'Element 'http://ideablade.com/EntityModel:NextIdGenerator' contains
data from a type that maps to the name 'http://schemas.datacontract.org/2004/07/OrianaHouse.CMIS.UI:NumericIdGenerator'.

The deserializer has no knowledge of any type that maps to this name.
Consider using a DataContractResolver or add the type corresponding to 'NumericIdGenerator' to the list of known types -
for example, by using the KnownTypeAttribute attribute or by adding it to the list of known types passed to DataContractSerializer.'.

Please see InnerException for more details."

 

I'm guessing here that my NumericIdGenerator is not being found on the server side?  This leads me once again to one of the questions I asked previously in this thread.  Where do I need to place my NumericIdGenerator so that it can be seen on both the Client and Server side?

 

Currently I have the NumericIdGenerator in my main interface assembly on the Client side.  This assembly contains a reference to my domain model assembly named "CMISModelSL".

 

On the server side I went ahead and just placed the NumericIdGenerator in the data model itself called "CMISModel".  I tried the KnownTypeAttribute and that didn't make a difference.

 

Below are screenshots of my project structure:

 

 

 

 

The IdGenerator should be defined on both client and server sides, and an instance holding the temporary Ids will be transmitted from the client to the server when doing a SaveChanges.   The class should be marked with a DataContract attribute, and any members needed on the server, such as temporary ids, should be marked with the DataMember attribute.  These members should also be public in Silverlight applications.  You don't need to mark up the class as a known type. 

 

We have a sample NumericIdGenerator for use in Silverlight applications in the MiniDemos for Business Object Persistence (although this might not be available until version 6.0.4 ships - if you can't find it in your Learning Resources we can send it to you).