How to: Inherit from Existing Windows Forms Controls

Artykuł
02/04/2013

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 Button, your new control would look and act exactly like a standard 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 OnPaint method.

Note

The dialog boxes and menu commands you see might differ from those described in Help depending on your active settings or edition. To change your settings, choose Import and Export Settings on the Tools menu. For more information, see Working with Settings.

To create an inherited control

Create a new Windows Forms Application project.
From the Project menu, choose Add New Item.

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

A new custom control is added to your project.
If you 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.
If you are using C#, open CustomControl1.cs in the Code Editor.
Locate the class declaration, which inherits from Control.
Change the base class to the control that you want to inherit from.

For example, if you want to inherit from Button, change the class declaration to the following:
```
Partial Class CustomControl1
    Inherits System.Windows.Forms.Button
```
```
public partial class CustomControl1 : System.Windows.Forms.Button
```
If you are using Visual Basic, save and close CustomControl1.Designer.vb. Open CustomControl1.vb in the Code Editor.
Implement any custom methods or properties that your control will incorporate.
If you want to modify the graphical appearance of your control, override the OnPaint method.

Note

Overriding OnPaint will not allow you to modify the appearance of all controls. Those controls that have all of their painting done by Windows (for example, TextBox) never call their OnPaint 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 OnPaint 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 OnPaint 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).
}
```
Save and test your control.

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How to: Inherit from Existing Windows Forms Controls

To create an inherited control

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