using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; namespace MyCompany.WinUI.MyClasses { public class MyComboBox : System.Windows.Forms.ComboBox { // code here } public class MyTextBox : System.Windows.Forms.TextBox { // code here } public class MyButton : System.Windows.Forms.Button { // code here } }That's it. These controls can't be sub-classed visually, but as you can see, it's easy enough to do it in code. I have all the basic controls sub-classed in one class library file. Once they're added to the ToolBox, then can be dragged onto any design surface in the IDE.