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how-to-inherit-from-existing-windows-forms-controls.md

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Inherit from Existing Controls
Learn how to inherit from existing controls so that another control has all of its functionality and visual properties.
03/30/2017
csharp
vb
inheritance [Windows Forms], Windows Forms custom controls
custom controls [Windows Forms], inheritance
1e1fc8ea-c615-4cf0-a356-16d6df7444ab

How to: Inherit from Existing Windows Forms Controls

If you want to extend the functionality of an existing control, you can create a control derived from an existing control through inheritance. When inheriting from an existing control, you inherit all of the functionality and visual properties of that control. For example, if you were creating a control that inherited from xref:System.Windows.Forms.Button, your new control would look and act exactly like a standard xref:System.Windows.Forms.Button control. You could then extend or modify the functionality of your new control through the implementation of custom methods and properties. In some controls, you can also change the visual appearance of your inherited control by overriding its xref:System.Windows.Forms.Control.OnPaint%2A method.

To create an inherited control

  1. In Visual Studio, create a new Windows Forms Application project.

  2. From the Project menu, choose Add New Item.

    The Add New Item dialog box appears.

  3. In the Add New Item dialog box, double-click Custom Control.

    A new custom control is added to your project.

  4. If you're using:

    • Visual Basic, at the top of Solution Explorer, click Show All Files. Expand CustomControl1.vb and then open CustomControl1.Designer.vb in the Code Editor.
    • C#, open CustomControl1.cs in the Code Editor.

  5. Locate the class declaration, which inherits from xref:System.Windows.Forms.Control.

  6. Change the base class to the control that you want to inherit from.

    For example, if you want to inherit from xref:System.Windows.Forms.Button, change the class declaration to the following:

    Partial Class CustomControl1
    Inherits System.Windows.Forms.Button
    public partial class CustomControl1 : System.Windows.Forms.Button

  7. If you are using Visual Basic, save and close CustomControl1.Designer.vb. Open CustomControl1.vb in the Code Editor.

  8. Implement any custom methods or properties that your control will incorporate.

  9. If you want to modify the graphical appearance of your control, override the xref:System.Windows.Forms.Control.OnPaint%2A method.

    [!NOTE] Overriding xref:System.Windows.Forms.Control.OnPaint%2A will not allow you to modify the appearance of all controls. Those controls that have all of their painting done by Windows (for example, xref:System.Windows.Forms.TextBox) never call their xref:System.Windows.Forms.Control.OnPaint%2A method, and thus will never use the custom code. Refer to the Help documentation for the particular control you want to modify to see if the xref:System.Windows.Forms.Control.OnPaint%2A method is available. For a list of all the Windows Form Controls, see Controls to Use on Windows Forms. If a control does not have xref:System.Windows.Forms.Control.OnPaint%2A listed as a member method, you cannot alter its appearance by overriding this method. For more information about custom painting, see Custom Control Painting and Rendering.

    Protected Overrides Sub OnPaint(ByVal e As _
   System.Windows.Forms.PaintEventArgs)
   MyBase.OnPaint(e)
   ' Insert code to do custom painting.
   ' If you want to completely change the appearance of your control,
   ' do not call MyBase.OnPaint(e).
End Sub
    protected override void OnPaint(PaintEventArgs pe)
{
   base.OnPaint(pe);
   // Insert code to do custom painting.
   // If you want to completely change the appearance of your control,
   // do not call base.OnPaint(pe).
}

  10. Save and test your control.

See also