Database is being used by another process … but what process?

Question

I have written a very small C# program, that uses a very small SQL Server database, purely for some learning & testing purposes. The database is used in this one new pro

Answer 1

I think there is already SqlTestDB.mdf is attached. I have faced this problem before, simply go to Ms Sql server and detach the database then rebuild your connection at Server Explorer in Visual Studio.