How to: Respond to Selecting ListBoxControl's Items

• Aug 01, 2019
• 2 minutes to read

The ListBoxControl displays system color names. The following sample code handles the BaseListBoxControl.SelectedIndexChanged event to change the form’s background color to the color whose name is currently selected. The formBkColors hashtable is created for this purpose. Its key is a string representing the system color name. The value, in turn, represents the proper color object. Hence, when a desired color name is selected, the proper color is assigned to the form’s BackColor property.

The image below demonstrates the ListBoxControl‘s look & feel after sample code execution.

C#

// Creates and initializes a new Hashtable.
Hashtable formBkColors = new Hashtable();
// Creates an array containing system colors
Color[] sysColors = {
                           SystemColors.ActiveCaption,
                           SystemColors.ActiveCaptionText,
                           SystemColors.AppWorkspace,
                           SystemColors.Control,
                           SystemColors.ControlDark,
                           SystemColors.ControlLight,
                           SystemColors.ControlText,
                           SystemColors.Desktop,
                           SystemColors.Highlight,
                           SystemColors.InactiveBorder,
                           SystemColors.InactiveCaption,
                           SystemColors.Info,
                           SystemColors.InfoText,
                           SystemColors.Menu,
                           SystemColors.MenuText,
                           SystemColors.ScrollBar,
                           SystemColors.Window,
                           SystemColors.WindowFrame
                        };
// ...
for(int i = 0; i < sysColors.Length; i++){
   // Fills the hashtable
   formBkColors[sysColors[i].Name] = sysColors[i];
   // Populates the ListBoxControl items collection
   listBoxControl1.Items.Add(sysColors[i].Name);
}
private void listBoxControl1_SelectedIndexChanged(object sender, System.EventArgs e) {
   this.BackColor = (Color)formBkColors[(sender as ListBoxControl).Text];
}

VB.NET

' Creates and initializes a new Hashtable.
Dim formBkColors As New Hashtable()
' Creates an array containing system colors
Dim sysColors() As Color = 
  New Color() {SystemColors.ActiveCaption, SystemColors.ActiveCaptionText, _
  SystemColors.AppWorkspace, SystemColors.Control, SystemColors.ControlDark, _
  SystemColors.ControlLight, SystemColors.ControlText, SystemColors.Desktop, _
  SystemColors.Highlight, SystemColors.InactiveBorder, SystemColors.InactiveCaption, _
  SystemColors.Info, SystemColors.InfoText, SystemColors.Menu, SystemColors.MenuText, _
  SystemColors.ScrollBar, SystemColors.Window, SystemColors.WindowFrame}
' ...
Dim i As Integer
For i = 0 To sysColors.Length - 1
   ' Fills the hashtable
   formBkColors(sysColors(i).Name) = sysColors(i)
   ' Populates the ListBoxControl items collection
   ListBoxControl1.Items.Add(sysColors(i).Name)
Next i

Private Sub ListBoxControl1_SelectedIndexChanged(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles ListBoxControl1.SelectedIndexChanged
   Me.BackColor = CType(formBkColors((TryCast(sender, ListBoxControl)).Text), Color)
End Sub