Consider the following scenario:
You have a Transaction Integrator (TI) assembly that was created in Microsoft Visual Studio.
The TI assembly includes a method that has a return value data type of Union.
In this scenario, an "index out of bound" error occurs when you try to view the Host Data Definition tab of the Transaction Integrator assembly in Visual Studio.
Cumulative update information
The fix that resolves this problem is included in Cumulative Update 1 for Host Integration Server 2013.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.