To Work with Data Access Classes
You can use Microsoft Visual Studio to work with a data access class (DAC) that has been added to a customization project.
A customization project can contain code for a DAC in the following item types (see Supported DAC Extension Formats for details):
  - As a DAC item with XML data for an existing DAC
 - As a Code item with the code of an existing DAC extension
 - As a Code item with the code of a custom DAC
 - In a File item that keeps a .dll file of the extension library that contains the binary code of a DAC extension or custom DAC
 
Once a customization project is published, you can use Visual Studio to develop, modify, and debug the customization code of a Code item on the fly. However, you cannot use this approach for a DAC item.
If you need to work in Visual Studio with the code of the DAC whose changeset is added to a
   customization project as a DAC item in XML format, perform the following actions:
 - Follow the instructions described in To Convert a DAC Item to a Code Item to convert the item to the Code item.
 - Follow the instructions described in To Work with a Code Item to change the code of the DAC extension.
 
