Using Context Menus

Table of Contents Getting a Command List Implementing a Command List Provider Importing a Command List Displaying the Context Menu Topics in this section

Context menus display a list of commands, typically in response to mouse clicks on a control.

For WinForms, the ICommandService interface provides this method to display a context menu for commands, given a collection of commands:

void RunContextMenu(IEnumerable<object> commandTags, Point screenPoint);

This section discusses how to get the command list and display it in a context menu.

Getting a Command List

The IContextMenuCommandProvider interface contains the following method to collect commands appropriate for a context:

IEnumerable<object> GetCommands(object context, object target);

The parameter target is the object clicked on, and context is the context containing target.

Thus any class implementing IContextMenuCommandProvider can provide a collection of commands for a given context.

Implementing a Command List Provider

This example from StandardEditCommands provides a list of commands, if the provided context is a selection and instancing context and thus appropriate for editing:

IEnumerable<object> IContextMenuCommandProvider.GetCommands(object context, object clicked)
{
    ISelectionContext selectionContext = context.As<ISelectionContext>();
    IInstancingContext instancingContext = context.As<IInstancingContext>();
    if ((selectionContext != null) && (instancingContext != null))
    {
        return new object[]
            {
                StandardCommand.EditCut,
                StandardCommand.EditCopy,
                StandardCommand.EditPaste,
                StandardCommand.EditDelete,
            };
    }

    return EmptyEnumerable<object>.Instance;
}

Importing a Command List

The ControlHostService for WinForms has the following import:

[ImportMany]
private IEnumerable<Lazy<IContextMenuCommandProvider>> m_contextMenuCommandProviders;

This allows the component to get a collection of objects on which it can call IContextMenuCommandProvider.GetCommands() to get a list of commands appropriate to the context. A variety of components export IContextMenuCommandProvider, including several that create standard commands, such as StandardEditCommands shown previously and DefaultTabCommands.

Displaying the Context Menu

ControlHostService for WinForms uses the collection contextMenuCommandProviders it imported, as shown previously, to implement this method that displays a context menu in response to a right-click event:

private void dockPaneStrip_MouseUp(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Right)
    {
        DockPaneStripBase dockPaneStrip = sender as DockPaneStripBase;

        ControlInfo info = FindControlInfo(m_activeDockContent.Controls[0]);
        IEnumerable<object> commands =
            m_contextMenuCommandProviders.GetCommands(null, info);

        Point screenPoint = dockPaneStrip.PointToScreen(new Point(e.X, e.Y));

        m_commandService.RunContextMenu(commands, screenPoint);
    }
}

Topics in this section