using DevExpress.XtraBars;
using DevExpress.XtraBars.Localization;

private void ribbonControl1_ShowCustomizationMenu(object sender, DevExpress.XtraBars.Ribbon.RibbonCustomizationMenuEventArgs e) {
    // Check if the context menu is invoked after a link is right-clicked.
    if (e.Link == null) return;
    // Locate and hide the "Add to Quick Access Toolbar" command in the context menu
    BarItemLink linkAddToQat = e.CustomizationMenu.ItemLinks.Where(link => link.Caption == BarLocalizer.Active.GetLocalizedString(BarString.RibbonToolbarAdd)).FirstOrDefault();
    linkAddToQat.Visible = false;

    // Check if a custom "About" command has already been created.
    BarItemLink menuAboutCommand = e.CustomizationMenu.ItemLinks.Where(link => link.Caption == "About").FirstOrDefault();
    // Add the "About" command.
    if (menuAboutCommand == null) {
        menuAboutCommand = e.CustomizationMenu.AddItem(GetAboutCommand());
        // Add a separator before the command.
        menuAboutCommand.BeginGroup = true;
    }
}

BarItem biAbout;
BarItem GetAboutCommand() {
    if (biAbout == null) {
        biAbout = new BarButtonItem();
        biAbout.Caption = "About";
        biAbout.ItemClick += new ItemClickEventHandler(biAbout_ItemClick);
        ribbonControl1.Items.Add(biAbout);
    }
    return biAbout;
}
// The method invoked when the "About" command is clicked.
void biAbout_ItemClick(object sender, ItemClickEventArgs e) {
    MessageBox.Show("About");
}

Imports DevExpress.XtraBars
Imports DevExpress.XtraBars.Localization

Private Sub RibbonControl1_ShowCustomizationMenu(sender As Object, e As DevExpress.XtraBars.Ribbon.RibbonCustomizationMenuEventArgs) Handles RibbonControl1.ShowCustomizationMenu
    ' Check if the context menu is invoked after a link is right-clicked.
    If e.Link Is Nothing Then Return
    ' Locate and hide the "Add to Quick Access Toolbar" command in the context menu
    Dim linkAddToQat As BarItemLink = e.CustomizationMenu.ItemLinks.Where(Function(link) link.Caption = BarLocalizer.Active.GetLocalizedString(BarString.RibbonToolbarAdd)).FirstOrDefault()
    linkAddToQat.Visible = False
    ' Check if a custom "About" command has already been created.
    Dim menuAboutCommand As BarItemLink = e.CustomizationMenu.ItemLinks.Where(Function(link) link.Caption = "About").FirstOrDefault()
    ' Add the "About" command.
    If menuAboutCommand Is Nothing Then
        menuAboutCommand = e.CustomizationMenu.AddItem(GetAboutCommand())
        ' Add a separator before the command.
        menuAboutCommand.BeginGroup = True
    End If
End Sub

Private biAbout As BarItem = Nothing
Private Function GetAboutCommand() As BarItem
    If biAbout Is Nothing Then
        biAbout = New BarButtonItem()
        biAbout.Caption = "About"
        AddHandler biAbout.ItemClick, AddressOf biAbout_ItemClick
        RibbonControl1.Items.Add(biAbout)
    End If
    Return biAbout
End Function

' The method invoked when the "About" command is clicked.
Private Sub biAbout_ItemClick(ByVal sender As System.Object,
  ByVal e As DevExpress.XtraBars.ItemClickEventArgs)
    MessageBox.Show("About")
End Sub