Yes. I use the data adapter wizard then would generate the dataset. If I make modification in the code or on the form not even relating to the data set, it gets removed from the form aftere switching between form and code editor. A friend of mine ask me to delete the bin and obj folders. This works but temporarily. And strangely, the name of the project "Payroll" would be added to the dataset name for instance, the dataset is called DsDepartment, it turns to be "Payroll.DsDepartment", I would then have to remove the Payroll manually.