Article ID: 983056 - View products that this article applies to.
After you specify an Enum type value as the default value of an input parameter in an External Content Type Update method in Microsoft Office SharePoint Designer, you cannot enter into the edit mode for the updated method.
This issue occurs because the Enum type value that you specify for the Update method is not in the Global Assembly Cache (GAC) list. Therefore, the Office SharePoint Designer throws a null reference exception. Additionally, the operation editor does not start.
To resolve this issue, delete and then re-create the Update method in Office SharePoint Designer.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.