If you're using Visual Studio to debug, compile and run your program, for example if you followed this tutorial on this site for setting up C#, this one to be exact link then you need to manually copy System.Data.Common.dll, System.Data.dll, System.Text.Encoding.CodePages.dll, System.Text.Encoding.dll from the runtime folder to your resource folder each time after you compile it. Or you can just setup a build event in VS to do it for you.