When you use a Windows Form as an MDI parent form, the Application Background color setting in Windows Control Panel, not the form's BackgroundColor property, determines the background color of the form. The following steps demonstrate how to programmatically change the MDI parent form's background color to another color.
- Create a new Visual Basic .NET or Visual Basic 2005 Windows application. Form1 is created by default.
Note The code should be changed in Visual Basic 2005. If you create a new form named Form1 in Visual Basic 2005, you have a Form1.vb file for your code and a Form1.Designer.vb file that contains the section that is automatically generated. The Windows Forms Designer uses the partial keyword to divide the implementation of Form1 into two separate files. This behavior prevents the designer-emitted code from being interspersed with your code.
For more information about the new Visual Basic 2005 language enhancements, visit the following Microsoft Web site:
- Click the form, and then, on the View menu, select Properties Window to view the properties for the form.
- Set the BackColor property to the color that you want (such as LightBlue).
- Set the IsMDIContainer property to True. Note that the background color of the form changes to the color that the Application Background color is set to in Control Panel.
- Set the WindowState property to Maximized.
- Double-click the form to view its code window.
- Paste the following code into the form's Load event handler:
Dim ctl As Control
Dim ctlMDI As MdiClient
' Loop through all of the form's controls looking
' for the control of type MdiClient.
For Each ctl In Me.Controls
' Attempt to cast the control to type MdiClient.
ctlMDI = CType(ctl, MdiClient)
' Set the BackColor of the MdiClient control.
ctlMDI.BackColor = Me.BackColor
Catch exc As InvalidCastException
' Catch and ignore the error if casting failed.
' Display a child form to show this is still an MDI application.
Dim frm As New Form2()
frm.MdiParent = Me
- On the Project menu, click Add Windows Form.
- Accept the default name Form2.vb, and then click Open.
- Press F5 to run the application.