You may receive one of the following errors from Crystal Reports:
Unknown Database Connector Error
The dialog box will either be titled “SAP Crystal Reports ActiveX Designer” or “Crystal Report Windows Forms Viewer”.
This can occur for a few reasons.
You are missing a reference in your Visual Studio project. The Crystal Reports project for Visual Studio 2010 sometimes does not add the reference to “Crystal Reports for .Net” (in my case, version 13.0.2000.0). Right click on your project in the Solution Explorer, choose “Add Reference” and add “Crystal Reports for .Net” which is version 13.0.2000.0 for Crystal Reports 2010. Now, when this dialog closes, click on “Show All Files” in the “Solution Explorer”, expand “References” and make sure that “CrystalDecisions.Data.AdoDotNetInterop” is listed. This was the key for me getting connected through Visual Studio.
If you are connecting to Oracle, make sure that you have the latest drivers from them. It wouldn’t hurt to install both ODP.Net and their native ODBC drivers. You will need the ODP.Net to connect through the .Net Framework in code, but you will need the ODBC drivers through Crystal.