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Comment : implémenter un concepteur pour un contrôle

Cette rubrique décrit comment implémenter un concepteur (HelpLabelDesigner) pour le contrôle de fournisseur d'extendeurs HelpLabel, décrit dans Comment : implémenter un fournisseur d'extendeurs HelpLabel. Ce concepteur est une classe imbriquée dans le contrôle HelpLabel. L'exemple de code de concepteur illustre les points suivants :

  • HelpLabelDesigner dérive de ControlDesigner.

  • HelpLabelDesigner fournit un verbe de concepteur en substituant la propriété Verbs spécifiée dans l'interface IDesigner. Au moment du design, les verbes apparaissent sous la forme de commandes sur l'objet associé au concepteur. Pour plus d'informations, consultez Verbes de concepteur.

  • HelpLabelDesigner ajoute une propriété au moment du design (TrackSelection) à HelpLabel en substituant la méthode PreFilterProperties spécifiée par l'interface IDesignerFilter. Pour plus d'informations sur l'ajout ou le remplacement de propriétés et d'événements, consultez Filtrage des métadonnées.

Exemple

L'exemple de code suivant contient le code du concepteur.

Notes

Le code de concepteur suivant ne peut pas se compiler seul.Il vous faut compiler l'exemple dans Comment : implémenter un fournisseur d'extendeurs HelpLabel, qui contient le code du concepteur en tant que classe imbriquée.

' 
' <doc> 
' <desc> 
'      This is a designer for the HelpLabel.  This designer provides 
'      design time feedback for the label.  The help label responds 
'      to changes in the active control, but these events do not 
'      occur at design time.  In order to provide some usable feedback 
'      that the control is working the right way, this designer listens 
'      to selection change events and uses those events to trigger active 
'      control changes. 
' </desc> 
' </doc> 
'
<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
Public Class HelpLabelDesigner
    Inherits System.Windows.Forms.Design.ControlDesigner

    Private _trackSelection As Boolean = True 

    ' <summary> 
    ' This property is added to the control's set of properties in the method 
    ' PreFilterProperties below.  Note that on designers, properties that are 
    ' explictly declared by TypeDescriptor.CreateProperty can be declared as 
    ' private on the designer.  This helps to keep the designer's public 
    ' object model clean. 
    ' </summary>
    <DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)> _
    Private Property TrackSelection() As Boolean 
        Get 
            Return _trackSelection
        End Get 
        Set(ByVal Value As Boolean)
            _trackSelection = Value
            If _trackSelection Then 
                Dim ss As ISelectionService = CType(GetService(GetType(ISelectionService)), ISelectionService)
                If (ss IsNot Nothing) Then
                    UpdateHelpLabelSelection(ss)
                End If 
            Else 
                Dim helpLabel As HelpLabel = CType(Control, HelpLabel)
                If (helpLabel.activeControl IsNot Nothing) Then
                    helpLabel.activeControl = Nothing
                    helpLabel.Invalidate()
                End If 
            End If 
        End Set 
    End Property 

    Public Overrides ReadOnly Property Verbs() As DesignerVerbCollection
        Get 
            Dim myVerbs() As DesignerVerb = {New DesignerVerb("Sample Verb", AddressOf OnSampleVerb)}
            Return New DesignerVerbCollection(myVerbs)
        End Get 
    End Property 

    ' 
    ' <doc> 
    ' <desc> 
    '      Overrides Dispose.  Here we remove our handler for the selection changed 
    '      event.  With designers, it is critical that they clean up any events they 
    '      have attached.  Otherwise, during the course of an editing session many 
    '      designers might get created and never destroyed. 
    ' </desc> 
    ' </doc> 
    ' 
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then 
            Dim ss As ISelectionService = CType(GetService(GetType(ISelectionService)), ISelectionService)
            If (ss IsNot Nothing) Then 
                RemoveHandler ss.SelectionChanged, AddressOf OnSelectionChanged
            End If 
        End If 
        MyBase.Dispose(disposing)
    End Sub 

    ' 
    ' <doc> 
    ' <desc> 
    '       Overrides initialize.  Here we add an event handler to the selection service. 
    '      Notice that we are very careful not to assume that the selection service is 
    '      available.  It is entirely optional that a service is available and you should 
    '      always degrade gracefully if a service cannot be found. 
    ' </desc> 
    ' </doc> 
    ' 
    Public Overrides Sub Initialize(ByVal component As IComponent)
        MyBase.Initialize(component)

        Dim ss As ISelectionService = CType(GetService(GetType(ISelectionService)), ISelectionService)
        If (ss IsNot Nothing) Then 
            AddHandler ss.SelectionChanged, AddressOf OnSelectionChanged
        End If 
    End Sub 

    Private Sub OnSampleVerb(ByVal sender As Object, ByVal e As EventArgs)
        MessageBox.Show("You have just invoked a sample verb.  Normally, this would do something interesting.")
    End Sub 

    ' 
    ' <doc> 
    ' <desc> 
    '      The handler for the selection change event.  Here we update the active control within 
    '      the help label. 
    ' </desc> 
    ' </doc> 
    ' 
    Private Sub OnSelectionChanged(ByVal sender As Object, ByVal e As EventArgs)
        If _trackSelection Then 
            Dim ss As ISelectionService = CType(sender, ISelectionService)
            UpdateHelpLabelSelection(ss)
        End If 
    End Sub 

    Protected Overrides Sub PreFilterProperties(ByVal properties As IDictionary)
        ' Always call base first in PreFilter* methods, and last in PostFilter* 
        ' methods. 
        MyBase.PreFilterProperties(properties)

        ' We add a design-time property called TrackSelection that is used to track 
        ' the active selection.  If the user sets this to true (the default), then 
        ' we will listen to selection change events and update the control's active 
        ' control to point to the current primary selection.
        properties("TrackSelection") = TypeDescriptor.CreateProperty( _
           Me.GetType(), _
           "TrackSelection", _
           GetType(Boolean), _
           New Attribute() {CategoryAttribute.Design})
    End Sub 

    ' <summary> 
    ' This is a helper method that, given a selection service, will update the active control 
    ' of the help label with the currently active selection. 
    ' </summary> 
    ' <param name="ss"></param> 
    Private Sub UpdateHelpLabelSelection(ByVal ss As ISelectionService)
        Dim c As Control = CType(ss.PrimarySelection, Control)
        Dim helpLabel As HelpLabel = CType(Control, HelpLabel)
        If (c IsNot Nothing) Then
            helpLabel.activeControl = c
            helpLabel.Invalidate()
        Else 
            If (helpLabel.activeControl IsNot Nothing) Then
                helpLabel.activeControl = Nothing
                helpLabel.Invalidate()
            End If 
        End If 
    End Sub 

    Public Sub New()

    End Sub 
End Class
        // 
        // <doc> 
        // <desc> 
        //      This is a designer for the HelpLabel.  This designer provides 
        //      design time feedback for the label.  The help label responds 
        //      to changes in the active control, but these events do not 
        //      occur at design time.  In order to provide some usable feedback 
        //      that the control is working the right way, this designer listens 
        //      to selection change events and uses those events to trigger active 
        //      control changes. 
        // </desc> 
        // </doc> 
        //
        [System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name = "FullTrust")] 
        public class HelpLabelDesigner : System.Windows.Forms.Design.ControlDesigner 
        {

            private bool trackSelection = true;

            /// <summary> 
            /// This property is added to the control's set of properties in the method 
            /// PreFilterProperties below.  Note that on designers, properties that are 
            /// explictly declared by TypeDescriptor.CreateProperty can be declared as 
            /// private on the designer.  This helps to keep the designer's publi 
            /// object model clean. 
            /// </summary>
            [DesignerSerializationVisibility( DesignerSerializationVisibility.Hidden )]
            private bool TrackSelection
            {
                get
                {
                    return trackSelection;
                }
                set
                {
                    trackSelection = value;
                    if (trackSelection)
                    {
                        ISelectionService ss = (ISelectionService)GetService(typeof(ISelectionService));
                        if (ss != null)
                        {
                            UpdateHelpLabelSelection(ss);
                        }
                    }
                    else
                    {
                        HelpLabel helpLabel = (HelpLabel)Control;
                        if (helpLabel.activeControl != null)
                        {
                            helpLabel.activeControl = null;
                            helpLabel.Invalidate();
                        }
                    }
                }
            }

            public override DesignerVerbCollection Verbs
            {
                get
                {
                    DesignerVerb[] verbs = new DesignerVerb[] {
                                                                  new DesignerVerb("Sample Verb", new EventHandler(OnSampleVerb))
                                                              };
                    return new DesignerVerbCollection(verbs);
                }
            }

            // 
            // <doc> 
            // <desc> 
            //      Overrides Dispose.  Here we remove our handler for the selection changed 
            //      event.  With designers, it is critical that they clean up any events they 
            //      have attached.  Otherwise, during the course of an editing session many 
            //      designers may get created and never destroyed. 
            // </desc> 
            // </doc> 
            // 
            protected override void Dispose(bool disposing) 
            {
                if (disposing) 
                {
                    ISelectionService ss = (ISelectionService)GetService(typeof(ISelectionService));
                    if (ss != null) 
                    {
                        ss.SelectionChanged -= new EventHandler(OnSelectionChanged);
                    }
                }

                base.Dispose(disposing);
            }

            // 
            // <doc> 
            // <desc> 
            //       Overrides initialize.  Here we add an event handler to the selection service. 
            //      Notice that we are very careful not to assume that the selection service is 
            //      available.  It is entirely optional that a service is available and you should 
            //      always degrade gracefully if a service could not be found. 
            // </desc> 
            // </doc> 
            // 
            public override void Initialize(IComponent component) 
            {
                base.Initialize(component);

                ISelectionService ss = (ISelectionService)GetService(typeof(ISelectionService));
                if (ss != null) 
                {
                    ss.SelectionChanged += new EventHandler(OnSelectionChanged);
                }
            }

            private void OnSampleVerb(object sender, EventArgs e)
            {
                MessageBox.Show("You have just invoked a sample verb.  Normally, this would do something interesting.");
            }

            // 
            // <doc> 
            // <desc> 
            //      Our handler for the selection change event.  Here we update the active control within 
            //      the help label. 
            // </desc> 
            // </doc> 
            // 
            private void OnSelectionChanged(object sender, EventArgs e) 
            {
                if (trackSelection)
                {
                    ISelectionService ss = (ISelectionService)sender;
                    UpdateHelpLabelSelection(ss);
                }
            }

            protected override void PreFilterProperties(IDictionary properties)
            {
                // Always call base first in PreFilter* methods, and last in PostFilter* 
                // methods. 
                base.PreFilterProperties(properties);

                // We add a design-time property called "TrackSelection" that is used to track
                // the active selection.  If the user sets this to true (the default), then 
                // we will listen to selection change events and update the control's active 
                // control to point to the current primary selection.
                properties["TrackSelection"] = TypeDescriptor.CreateProperty(
                    this.GetType(),        // the type this property is defined on 
                    "TrackSelection",    // the name of the property 
                    typeof(bool),        // the type of the property 
                    new Attribute[] {CategoryAttribute.Design});    // attributes
            }

            /// <summary> 
            /// This is a helper method that, given a selection service, will update the active control 
            /// of our help label with the currently active selection. 
            /// </summary> 
            /// <param name="ss"></param>
            private void UpdateHelpLabelSelection(ISelectionService ss)
            {
                Control c = ss.PrimarySelection as Control;
                HelpLabel helpLabel = (HelpLabel)Control;
                if (c != null)
                {
                    helpLabel.activeControl = c;
                    helpLabel.Invalidate();
                }
                else
                {
                    if (helpLabel.activeControl != null)
                    {
                        helpLabel.activeControl = null;
                        helpLabel.Invalidate();
                    }
                }
            }
        }

Voir aussi

Tâches

Comment : implémenter un fournisseur d'extendeurs HelpLabel

Autres ressources

Concepteurs personnalisés

Extension de la prise en charge au moment du design