public event EventHandler<PopupMenuShowingEventArgs> PopupMenuShowing

Public Event PopupMenuShowing As EventHandler(Of PopupMenuShowingEventArgs)

<dxsps:SpreadsheetControl x:Name="spreadsheetControl" 
                          PopupMenuShowing="spreadsheetControl_PopupMenuShowing"/>

using DevExpress.Xpf.Bars;
using DevExpress.Xpf.Spreadsheet;
using DevExpress.Xpf.Spreadsheet.Menu;
using DevExpress.XtraSpreadsheet.Commands;
// ... 

private void spreadsheetControl_PopupMenuShowing(object sender, PopupMenuShowingEventArgs e) {
    // Check whether the event is raised for a spreadsheet cell.
    if (e.MenuType == SpreadsheetMenuType.Cell) {

        // Create a menu item to merge selected cells
        // and bind this item to the spreadsheet command.
        e.Customizations.Add(new BarButtonItem() {
            Command = SpreadsheetUICommand.EditingMergeAndCenterCells,
            Content = "Merge Cells",
            CommandParameter = spreadsheetControl
        });

        // Create a custom menu item to highlight selected cells.
        var menuItem = new BarButtonItem();
        menuItem.Name = "highlightCellsItem";
        menuItem.Content = "Highlight Cells";
        menuItem.ItemClick += MenuItem_ItemClick;
        e.Customizations.Add(menuItem);
    }

    // Remove the "Insert Comment" item from the menu.
    e.Customizations.Add(new RemoveSpreadsheetCommandAction() {
        Id = SpreadsheetCommandId.ReviewInsertCommentContextMenuItem
    });

    // Remove the "Hyperlink" item from the menu.
    e.Customizations.Add(new RemoveSpreadsheetCommandAction() {
        Id = SpreadsheetCommandId.InsertHyperlinkContextMenuItem
    });
}

private void MenuItem_ItemClick(object sender, ItemClickEventArgs e) {
    // Fill selected cells with the yellow color.
    spreadsheetControl.Selection.FillColor = System.Drawing.Color.Yellow;
}

Imports DevExpress.Xpf.Bars
Imports DevExpress.Xpf.Spreadsheet
Imports DevExpress.Xpf.Spreadsheet.Menu
Imports DevExpress.XtraSpreadsheet.Commands
' ...

Private Sub spreadsheetControl_PopupMenuShowing(ByVal sender As Object, ByVal e As PopupMenuShowingEventArgs)
    ' Check whether the event is raised for a spreadsheet cell.
    If e.MenuType = SpreadsheetMenuType.Cell Then

        ' Create a menu item to merge selected cells
        ' and bind this item to the spreadsheet command.
        e.Customizations.Add(New BarButtonItem() With {
            .Command = SpreadsheetUICommand.EditingMergeAndCenterCells,
            .Content = "Merge Cells",
            .CommandParameter = spreadsheetControl
        })

        ' Create a custom menu item to highlight selected cells.
        Dim menuItem As New BarButtonItem()
        menuItem.Name = "highlightCellsItem"
        menuItem.Content = "Highlight Cells"
        menuItem.ItemClick += MenuItem_ItemClick
        e.Customizations.Add(menuItem)
    End If

    ' Remove the "Insert Comment" item from the menu.
    e.Customizations.Add(New RemoveSpreadsheetCommandAction() With {
        .Id = SpreadsheetCommandId.ReviewInsertCommentContextMenuItem})

    ' Remove the "Hyperlink" item from the menu.
    e.Customizations.Add(New RemoveSpreadsheetCommandAction() With {
        .Id = SpreadsheetCommandId.InsertHyperlinkContextMenuItem})
End Sub

Private Sub MenuItem_ItemClick(ByVal sender As Object, ByVal e As ItemClickEventArgs)
    ' Fill selected cells with the yellow color.
    spreadsheetControl.Selection.FillColor = System.Drawing.Color.Yellow
End Sub

BarManager="{Binding ElementName=barManager1, Mode=OneTime}"
PopupMenuShowing="SpreadsheetControlPopupMenuShowing">
<dxsps:SpreadsheetControl.MenuCustomizations>

#line 33 "..\..\..\MainWindow.xaml"
this.spreadsheetControl1.PopupMenuShowing += new System.EventHandler<DevExpress.Xpf.Spreadsheet.Menu.PopupMenuShowingEventArgs>(this.SpreadsheetControlPopupMenuShowing);

#ExternalSource("..\..\MainWindow.xaml",33)
AddHandler Me.spreadsheetControl1.PopupMenuShowing, New System.EventHandler(Of DevExpress.Xpf.Spreadsheet.Menu.PopupMenuShowingEventArgs)(AddressOf Me.SpreadsheetControlPopupMenuShowing)