During testing of AVR for .NET 15.0 we found that a Visual Studio 2017 conflict causes issues with version 2.7 of the ADO.NET library. If you’re using that version of ADO.NET  in projects with AVR 15.x you will get a compiler error.

This error has nothing to do with AVR directly, as demonstrated by attempting to add a reference to ADO 2.7 to a C# console app project which fails showing the following error message box:

The ADO.NET error isn’t specific to AVR, it also occurs with C# and VB.NET.


To resolve this error, remove the 2.7 reference and add a fresh reference to a newer version of ADO before attempting to compile in VS 2017.

If after doing this you still encounter compiler errors about not being able to load the ADODB library:

  1. Exit Visual Studio
  2. Go to the solution folder
  3. Delete the hidden .vs directory (which caches VS information for the solution). See note below for more info.
  4. Restart Visual Studio and then compile your program
Deleting the hidden .vs directory

The .vs folder is hidden, so you must either configure your Windows Explorer to show hidden files and folders or: 

  1. Open a DOS command line
  2. Navigate to your project’s root directory
  3. Show all hidden folders with (to ensure you’re in the right folder)
    dir /a:hd 
  4. Delete the .vs directory with:
    rd .vs /s /q