WorkflowDesignerMessageFilter Class
Provides a base class for all workflow message filters.
Assembly: System.Workflow.ComponentModel (in System.Workflow.ComponentModel.dll)
The workflow designer provides a Strategy design pattern to create replaceable message filter objects to handle events.
Derive from the WorkflowDesignerMessageFilter class to create message filters that can respond to workflow designer events, such as drag operations, layout and paint operations, and other designer events. To add a custom message filter to the message filters chain, call the AddDesignerMessageFilter on the WorkflowView or override the MessageFilters virtual property on the custom root activity and add the custom message filter to the collection returned from the base class.
The following code example shows a custom designer message filter that derives from WorkflowDesignerMessageFilter. The class, named CustomMessageFilter, overrides a number of its base class methods including OnMouseDown, OnMouseMove, OnMouseUp, OnMouseDoubleClick, OnMouseEnter, OnMouseHover, OnMouseLeave, OnDragEnter, OnDragOver, and OnKeyDown.
This code example is part of the Basic Designer Hosting SDK Sample from the DesignerShell.cs file. For more information, see Basic Designer Hosting.
Friend NotInheritable Class CustomMessageFilter
Inherits WorkflowDesignerMessageFilter
#Region "Members and Constructor"
Private mouseDown As Boolean
Private serviceProvider As IServiceProvider
Private workflowView As WorkflowView
Private loader As WorkflowDesignerLoader
Public Sub New(ByVal provider As IServiceProvider, ByVal workflowView As WorkflowView, ByVal loader As WorkflowDesignerLoader)
Me.serviceProvider = provider
Me.workflowView = workflowView
Me.loader = loader
End Sub
#End Region
#Region "WorkflowDesignerMessageFilter Overridables"
Protected Overrides Function OnMouseDown(ByVal eventArgs As System.Windows.Forms.MouseEventArgs) As Boolean
' Allow other components to process this event by not returning true.
mouseDown = True
Return False
End Function
Protected Overrides Function OnMouseMove(ByVal eventArgs As System.Windows.Forms.MouseEventArgs) As Boolean
' Allow other components to process this event by not returning true.
If mouseDown Then
workflowView.ScrollPosition = New Point(eventArgs.X, eventArgs.Y)
End If
Return False
End Function
Protected Overrides Function OnMouseUp(ByVal eventArgs As MouseEventArgs) As Boolean
' Allow other components to process this event by not returning true.
mouseDown = False
Return False
End Function
Protected Overrides Function OnMouseDoubleClick(ByVal eventArgs As MouseEventArgs) As Boolean
mouseDown = False
Return True
End Function
Protected Overrides Function OnMouseEnter(ByVal eventArgs As MouseEventArgs) As Boolean
' Allow other components to process this event by not returning true.
mouseDown = False
Return False
End Function
Protected Overrides Function OnMouseHover(ByVal eventArgs As MouseEventArgs) As Boolean
' Allow other components to process this event by not returning true.
mouseDown = False
Return False
End Function
Protected Overrides Function OnMouseLeave() As Boolean
' Allow other components to process this event by not returning true.
mouseDown = False
Return False
End Function
Protected Overrides Function OnMouseWheel(ByVal eventArgs As MouseEventArgs) As Boolean
mouseDown = False
Return True
End Function
Protected Overrides Function OnMouseCaptureChanged() As Boolean
' Allow other components to process this event by not returning true.
mouseDown = False
Return False
End Function
Protected Overrides Function OnDragEnter(ByVal eventArgs As DragEventArgs) As Boolean
Return True
End Function
Protected Overrides Function OnDragOver(ByVal eventArgs As DragEventArgs) As Boolean
Return True
End Function
Protected Overrides Function OnDragLeave() As Boolean
Return True
End Function
Protected Overrides Function OnDragDrop(ByVal eventArgs As DragEventArgs) As Boolean
Return True
End Function
Protected Overrides Function OnGiveFeedback(ByVal gfbevent As GiveFeedbackEventArgs) As Boolean
Return True
End Function
Protected Overrides Function OnQueryContinueDrag(ByVal qcdevent As QueryContinueDragEventArgs) As Boolean
Return True
End Function
Protected Overrides Function OnKeyDown(ByVal eventArgs As KeyEventArgs) As Boolean
If eventArgs.KeyCode = Keys.Delete Then
Dim selectionService As ISelectionService = CType(serviceProvider.GetService(GetType(ISelectionService)), ISelectionService)
If selectionService IsNot Nothing AndAlso TypeOf selectionService.PrimarySelection Is CodeActivity Then
Dim codeActivityComponent As CodeActivity = CType(selectionService.PrimarySelection, CodeActivity)
Dim parentActivity As CompositeActivity = codeActivityComponent.Parent
If parentActivity IsNot Nothing Then
parentActivity.Activities.Remove(codeActivityComponent)
Me.ParentView.Update()
End If
loader.RemoveActivityFromDesigner(codeActivityComponent)
End If
End If
Return True
End Function
Protected Overrides Function OnKeyUp(ByVal eventArgs As KeyEventArgs) As Boolean
Return True
End Function
Protected Overrides Function OnShowContextMenu(ByVal menuPoint As Point) As Boolean
Return True
End Function
#End Region
End Class
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.