Classe ContextMenuProvider

Articolo
09/12/2008

Aggiornamento: novembre 2007

Definisce un set di voci di menu visualizzate in un menu di scelta rapida.

Spazio dei nomi: Microsoft.Windows.Design.Interaction
Assembly: Microsoft.Windows.Design.Extensibility (in Microsoft.Windows.Design.Extensibility.dll)

Sintassi

Public MustInherit Class ContextMenuProvider _
    Inherits FeatureProvider

Dim instance As ContextMenuProvider

public abstract class ContextMenuProvider : FeatureProvider

public ref class ContextMenuProvider abstract : public FeatureProvider

public abstract class ContextMenuProvider extends FeatureProvider

Note

Ereditare dalla classe ContextMenuProvider quando si desidera aggiungere una voce a un determinato menu di scelta rapida. Applicando i criteri, ad esempio PrimarySelectionPolicy e SelectionParentPolicy, è possibile controllare quando viene creato il provider di menu di scelta rapida.

L'esistenza di ContextMenuProvider è temporanea. Non presupporre che sarà persistente per lunghi periodi di tempo.

Esempi

Nell'esempio di codice seguente viene illustrato come derivare un tipo personalizzato dalla classe PrimarySelectionContextMenuProvider. Il tipo derivato implementa un menu di scelta rapida personalizzato che imposta la proprietà Background di un controllo in fase di progettazione. Per ulteriori informazioni, vedere Procedura dettagliata: creazione di una MenuAction.

Imports System
Imports System.Collections.Generic
Imports System.Text
Imports Microsoft.Windows.Design.Interaction
Imports System.Windows
Imports Microsoft.Windows.Design.Model
Imports System.Windows.Controls
Imports System.Windows.Media

' The CustomContextMenuProvider class provides two context menu items
' at design time. These are implemented with the MenuAction class.
Class CustomContextMenuProvider
    Inherits PrimarySelectionContextMenuProvider

    Private setBackgroundToBlueMenuAction As MenuAction
    Private clearBackgroundMenuAction As MenuAction

    ' The provider's constructor sets up the MenuAction objects 
    ' and the the MenuGroup which holds them.
    Public Sub New()

        ' Set up the MenuAction which sets the control's 
        ' background to Blue.
        setBackgroundToBlueMenuAction = New MenuAction("Blue")
        setBackgroundToBlueMenuAction.Checkable = True
        AddHandler setBackgroundToBlueMenuAction.Execute, AddressOf SetBackgroundToBlue_Execute

        ' Set up the MenuAction which sets the control's 
        ' background to its default value.
        clearBackgroundMenuAction = New MenuAction("Cleared")
        clearBackgroundMenuAction.Checkable = True
        AddHandler clearBackgroundMenuAction.Execute, AddressOf ClearBackground_Execute

        ' Set up the MenuGroup which holds the MenuAction items.
        Dim backgroundFlyoutGroup As New MenuGroup("SetBackgroundsGroup", "Set Background")

        ' If HasDropDown is false, the group appears inline, 
        ' instead of as a flyout. Set to true.
        backgroundFlyoutGroup.HasDropDown = True
        backgroundFlyoutGroup.Items.Add(setBackgroundToBlueMenuAction)
        backgroundFlyoutGroup.Items.Add(clearBackgroundMenuAction)
        Me.Items.Add(backgroundFlyoutGroup)

        ' The UpdateItemStatus event is raised immediately before 
        ' this provider shows its tabs, which provides the opportunity 
        ' to set states.
        AddHandler UpdateItemStatus, AddressOf CustomContextMenuProvider_UpdateItemStatus

    End Sub

    ' The following method handles the UpdateItemStatus event.
    ' It sets the MenuAction states according to the state
    ' of the control's Background property. This method is
    ' called before the context menu is shown.
    Sub CustomContextMenuProvider_UpdateItemStatus( _
        ByVal sender As Object, _
        ByVal e As MenuActionEventArgs)

        ' Turn everything on, and then based on the value 
        ' of the BackgroundProperty, selectively turn some off.
        clearBackgroundMenuAction.Checked = False
        clearBackgroundMenuAction.Enabled = True
        setBackgroundToBlueMenuAction.Checked = False
        setBackgroundToBlueMenuAction.Enabled = True

        ' Get a ModelItem which represents the selected control. 
        Dim selectedControl As ModelItem = _
            e.Selection.PrimarySelection

        ' Get the value of the Background property from the ModelItem.
        Dim backgroundProperty As ModelProperty = _
            selectedControl.Properties(Control.BackgroundProperty)

        ' Set the MenuAction items appropriately.
        If Not backgroundProperty.IsSet Then
            clearBackgroundMenuAction.Checked = True
            clearBackgroundMenuAction.Enabled = False
        ElseIf backgroundProperty.ComputedValue.Equals(Brushes.Blue) Then
            setBackgroundToBlueMenuAction.Checked = True
            setBackgroundToBlueMenuAction.Enabled = False
        End If

    End Sub

    ' The following method handles the Execute event. 
    ' It sets the Background property to its default value.
    Sub ClearBackground_Execute( _
        ByVal sender As Object, _
        ByVal e As MenuActionEventArgs)

        Dim selectedControl As ModelItem = e.Selection.PrimarySelection
        selectedControl.Properties(Control.BackgroundProperty).ClearValue()

    End Sub

    ' The following method handles the Execute event. 
    ' It sets the Background property to Brushes.Blue.
    Sub SetBackgroundToBlue_Execute( _
        ByVal sender As Object, _
        ByVal e As MenuActionEventArgs)

        Dim selectedControl As ModelItem = e.Selection.PrimarySelection
        selectedControl.Properties(Control.BackgroundProperty).SetValue(Brushes.Blue)

    End Sub

End Class

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Windows.Design.Interaction;
using System.Windows;
using Microsoft.Windows.Design.Model;
using System.Windows.Controls;
using System.Windows.Media;

namespace SliderAdornerLib
{
    // The CustomContextMenuProvider class provides two context menu items
    // at design time. These are implemented with the MenuAction class.
    class CustomContextMenuProvider : PrimarySelectionContextMenuProvider
    {
        private MenuAction setBackgroundToBlueMenuAction;
        private MenuAction clearBackgroundMenuAction;

        // The provider's constructor sets up the MenuAction objects 
        // and the the MenuGroup which holds them.
        public CustomContextMenuProvider()
        {   
            // Set up the MenuAction which sets the control's 
            // background to Blue.
            setBackgroundToBlueMenuAction = new MenuAction("Blue");
            setBackgroundToBlueMenuAction.Checkable = true;
            setBackgroundToBlueMenuAction.Execute += 
                new EventHandler<MenuActionEventArgs>(SetBackgroundToBlue_Execute);

            // Set up the MenuAction which sets the control's 
            // background to its default value.
            clearBackgroundMenuAction = new MenuAction("Cleared");
            clearBackgroundMenuAction.Checkable = true;
            clearBackgroundMenuAction.Execute += 
                new EventHandler<MenuActionEventArgs>(ClearBackground_Execute);

            // Set up the MenuGroup which holds the MenuAction items.
            MenuGroup backgroundFlyoutGroup = 
                new MenuGroup("SetBackgroundsGroup", "Set Background");

            // If HasDropDown is false, the group appears inline, 
            // instead of as a flyout. Set to true.
            backgroundFlyoutGroup.HasDropDown = true;
            backgroundFlyoutGroup.Items.Add(setBackgroundToBlueMenuAction);
            backgroundFlyoutGroup.Items.Add(clearBackgroundMenuAction);
            this.Items.Add(backgroundFlyoutGroup);

            // The UpdateItemStatus event is raised immediately before 
            // this provider shows its tabs, which provides the opportunity 
            // to set states.
            UpdateItemStatus += 
                new EventHandler<MenuActionEventArgs>(
                    CustomContextMenuProvider_UpdateItemStatus);
        }

        // The following method handles the UpdateItemStatus event.
        // It sets the MenuAction states according to the state
        // of the control's Background property. This method is
        // called before the context menu is shown.
        void CustomContextMenuProvider_UpdateItemStatus(
            object sender, 
            MenuActionEventArgs e)
        {
            // Turn everything on, and then based on the value 
            // of the BackgroundProperty, selectively turn some off.
            clearBackgroundMenuAction.Checked = false;
            clearBackgroundMenuAction.Enabled = true;
            setBackgroundToBlueMenuAction.Checked = false;
            setBackgroundToBlueMenuAction.Enabled = true;

            // Get a ModelItem which represents the selected control. 
            ModelItem selectedControl = e.Selection.PrimarySelection;

            // Get the value of the Background property from the ModelItem.
            ModelProperty backgroundProperty = 
                selectedControl.Properties[Control.BackgroundProperty];

            // Set the MenuAction items appropriately.
            if (!backgroundProperty.IsSet)
            {
                clearBackgroundMenuAction.Checked = true;
                clearBackgroundMenuAction.Enabled = false;
            }
            else if (backgroundProperty.ComputedValue == Brushes.Blue)
            {
                setBackgroundToBlueMenuAction.Checked = true;
                setBackgroundToBlueMenuAction.Enabled = false;
            }
        }

        // The following method handles the Execute event. 
        // It sets the Background property to its default value.
        void ClearBackground_Execute(
            object sender, 
            MenuActionEventArgs e)
        {
            ModelItem selectedControl = e.Selection.PrimarySelection;
            selectedControl.Properties[Control.BackgroundProperty].ClearValue();
        }

        // The following method handles the Execute event. 
        // It sets the Background property to Brushes.Blue.
        void SetBackgroundToBlue_Execute(
            object sender, 
            MenuActionEventArgs e)
        {
            ModelItem selectedControl = e.Selection.PrimarySelection;
            selectedControl.Properties[Control.BackgroundProperty].SetValue(Brushes.Blue);
        }
    }
}