public class MyBaseControl : System.Windows.Forms.UserControl { // code in here }Now, to sub-class it, you start out by doing it in code: Add a new class to your project, make it of type UserControl, then go into the code and change it from this:
public class MySubControl : System.Windows.Forms.UserControlto this:
public class MySubControl : MyBaseControlAt this point you can open your new sub-class up in the designer.