Symptoms
In Microsoft SharePoint Designer 2010, you use the External Content Type designer to generate methods on an external content type. However, when you use the GenerateAll option in the External Content Type designer, the wrong type name is assigned to the TypeDescriptors. These TypeDescriptors are marked as identifiers, and they have a nullable type. In this situation, the type names become non-nullable types.
More Information
The mapping of TypeDescriptors (whose type is nullable) to identifiers is not supported in Business Connectivity Services.
Status
Microsoft has confirmed that this is a problem in SharePoint Designer 2010.
