Beispiel eines Windows Forms-Designers
In diesem Thema wird ein Designer (HelpLabelDesigner) für das HelpLabel-Extenderprovidersteuerelement beschrieben, das unter Beispiel eines Extenderproviders in Windows Forms beschrieben wird. Der Designer ist eine geschachtelte Klasse im HelpLabel-Steuerelement. Die Möglichkeit zum Downloaden des Quellcodes und eine Demonstration der Verwendung des Beispiels finden Sie im HelpLabel-Beispiel in .NET-Beispiele - Windows Forms: Erstellen von Steuerelementen. Das Designer-Beispiel demonstriert folgende Aspekte:
HelpLabelDesignerwird von ControlDesigner abgeleitet.HelpLabelDesignerstellt ein Designerverb bereit, indem die Verbs-Eigenschaft außer Kraft gesetzt wird, die in der IDesigner-Schnittstelle angegeben ist. Zur Entwurfszeit erscheinen Verben als Befehle auf dem Objekt, das mit dem Designer verknüpft ist. Weitere Informationen finden Sie unter Designerverben.HelpLabelDesignerfügtHelpLabeleine Entwurfszeiteigenschaft (TrackSelection) hinzu, indem die PreFilterProperties-Methode außer Kraft gesetzt wird, die von der IDesignerFilter-Schnittstelle angegeben wird. Weitere Informationen zum Hinzufügen oder Ersetzen von Eigenschaften und Ereignissen finden Sie unter Filtern von Metadaten.
Das folgende Codefragment enthält den Code für den Designer.
**Hinweis **Der folgende Designercode kann allein nicht kompiliert werden. Kompilieren Sie stattdessen das Beispiel im Beispiel eines Extenderproviders in Windows Forms, das den Code für den Designer als geschachtelte Klasse enthält.
' <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>
'
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
' PreFilterProperties method. 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>
Private Property TrackSelection() As Boolean
Get
Return _trackSelection
End Get
Set
_trackSelection = value
If _trackSelection Then
Dim ss As ISelectionService = CType(GetService(GetType(ISelectionService)), ISelectionService)
If Not (ss Is Nothing) Then
UpdateHelpLabelSelection(ss)
End If
Else
Dim helpLabel As HelpLabel = CType(Control, HelpLabel)
If Not (helpLabel.activeControl Is 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 the 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(disposing As Boolean)
If disposing Then
Dim ss As ISelectionService = CType(GetService(GetType(ISelectionService)), ISelectionService)
If Not (ss Is 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(component As IComponent)
MyBase.Initialize(component)
Dim ss As ISelectionService = CType(GetService(GetType(ISelectionService)), ISelectionService)
If Not (ss Is Nothing) Then
AddHandler ss.SelectionChanged, AddressOf OnSelectionChanged
End If
End Sub
Private Sub OnSampleVerb(sender As Object, e As EventArgs)
MessageBox.Show("You have just invoked a sample verb. Normally, this would do something interesting.")
End Sub
'
' <doc>
' <desc>
' Our handler for the selection change event. Here we update the active control within
' the help label.
' </desc>
' </doc>
'
Private Sub OnSelectionChanged(sender As Object, e As EventArgs)
If _trackSelection Then
Dim ss As ISelectionService = CType(sender, ISelectionService)
UpdateHelpLabelSelection(ss)
End If
End Sub
Protected Overrides Sub PreFilterProperties(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 our help label with the currently active selection.
' </summary>
' <param name="ss"></param>
Private Sub UpdateHelpLabelSelection(ss As ISelectionService)
Dim c As Control = CType(ss.PrimarySelection, Control)
Dim helpLabel As HelpLabel = CType(Control, HelpLabel)
If Not (c Is Nothing) Then
helpLabel.activeControl = c
helpLabel.Invalidate()
Else
If Not (helpLabel.activeControl Is Nothing) Then
helpLabel.activeControl = Nothing
helpLabel.Invalidate()
End If
End If
End Sub
End Class
End Class
[C#]
//
// <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>
//
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
/// PreFilterProperties method. 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>
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 the 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 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 cannot 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>
// The 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 = (Control)ss.PrimarySelection;
HelpLabel helpLabel = (HelpLabel)Control;
if (c != null)
{
helpLabel.activeControl = c;
helpLabel.Invalidate();
}
else
{
if (helpLabel.activeControl != null)
{
helpLabel.activeControl = null;
helpLabel.Invalidate();
}
}
}
}
}
Siehe auch
Benutzerdefinierte Designer | Entwurfszeitunterstützung für Windows Forms