If you are having a problem saving the data you've entered into your TableAdapter's DataTable and you are using a local file database, check which file is being used as the database. I thought that I was accessing the .mdf file in my project directory, when it turns out that that file was being copied to the bin/Debug folder every time I ran the program in debug mode. This action was overwriting everything that I had thought was being saved to the database. There is a property setting in Solution Explorer when the database file is selected: Copy to Output Directory. If this property is set to Copy Always, as mine was by default, you will overwrite the database every time you run your program.