Daily Gem: VB / Silverlight / WP7 – Disable Pinch or Scroll in IE9 WebBrowser control

Step 1:  Create a helper class for the WebBrowser

Code Snippet

1. Imports System.Linq
2. Imports System.Windows
3. Imports System.Windows.Controls
4. Imports System.Windows.Input
5. Imports Microsoft.Phone.Controls
6.  
7.  
8. Public ClassWebBrowserHelper
9.     Private _browser As WebBrowser
10.  
11.     ”’ <summary>
12.     ”’ Gets or sets whether to suppress the scrolling of
13.     ”’ the WebBrowser control;
14.     ”’ </summary>
15.     PublicProperty ScrollDisabled() As Boolean
16.         Get
17.             Return m_ScrollDisabled
18.         EndGet
19.         Set(value As Boolean)
20.             m_ScrollDisabled = value
21.         EndSet
22.     EndProperty
23.     Private m_ScrollDisabled As Boolean
24.  
25.     PublicProperty PinchDisabled() As Boolean
26.         Get
27.             Return m_PinchDisabled
28.         EndGet
29.         Set(value As Boolean)
30.             m_PinchDisabled = value
31.         EndSet
32.     EndProperty
33.     Private m_PinchDisabled As Boolean
34.  
35.  
36.     PublicSub New(browser AsWebBrowser)
37.         _browser = browser
38.         AddHandler browser.Loaded, NewRoutedEventHandler(AddressOf browser_Loaded)
39.     EndSub
40.  
41.     PrivateSub browser_Loaded(sender As Object, e As RoutedEventArgs)
42.         Dim border = TryCast(_browser.Descendants(OfBorder)().Last(), Border)
43.  
44.         AddHandler border.ManipulationDelta, AddressOf Border_ManipulationDelta
45.         AddHandler border.ManipulationCompleted, AddressOf Border_ManipulationCompleted
46.     EndSub
47.  
48.     PrivateSub Border_ManipulationCompleted(sender AsObject, e AsManipulationCompletedEventArgs)
49.         ‘ optionally suppress pinch
50.         IfPinchDisabled Then
51.             If e.FinalVelocities.ExpansionVelocity.X <> 0.0 OrElse e.FinalVelocities.ExpansionVelocity.Y <> 0.0 Then
52.                 e.Handled = True
53.             EndIf
54.         EndIf
55.     EndSub
56.  
57.     PrivateSub Border_ManipulationDelta(sender AsObject, e AsManipulationDeltaEventArgs)
58.         ‘ optionally suppress pinch
59.         IfPinchDisabled Then
60.             If e.DeltaManipulation.Scale.X <> 0.0 OrElse e.DeltaManipulation.Scale.Y <> 0.0 Then
61.                 e.Handled = True
62.             EndIf
63.         EndIf
64.  
65.         ‘ optionally suppress scrolling
66.         IfScrollDisabled Then
67.             If e.DeltaManipulation.Translation.X <> 0.0 OrElse e.DeltaManipulation.Translation.Y <> 0.0 Then
68.                 e.Handled = True
69.             EndIf
70.         EndIf
71.     EndSub
72. End Class

Step 2: Add the LinqToVisualTree module, used by the above class to help in locating the browser’s border control

Code Snippet

1. Imports System.Linq
2. Imports System.Collections.Generic
3. Imports System.Windows
4. Imports System.Windows.Media
5. Imports System.Runtime.CompilerServices
6.  
7. <System.Runtime.CompilerServices.Extension()> _
8. Module LinqToVisualTree
9.     ”’ <summary>
10.     ”’ Adapts a DependencyObject to provide methods required for generate
11.     ”’ a Linq To Tree API
12.     ”’ </summary>
13.     PublicClass VisualTreeAdapter
14.         ImplementsILinqTree(OfDependencyObject)
15.         Private _item As DependencyObject
16.  
17.         PublicSub New(item AsDependencyObject)
18.             _item = item
19.         EndSub
20.         PublicFunction Children() AsIEnumerable(Of DependencyObject) Implements ILinqTree(OfDependencyObject).Children
21.             Dim list As New List(OfDependencyObject)
22.             DimchildrenCount As Integer = VisualTreeHelper.GetChildrenCount(_item)
23.             For i As Integer = 0 To childrenCount – 1
24.                 list.Add(VisualTreeHelper.GetChild(_item, i))
25.             Next
26.             Return list
27.         EndFunction
28.  
29.         PublicReadOnly Property Parent() AsDependencyObject ImplementsILinqTree(OfDependencyObject).Parent
30.             Get
31.                 ReturnVisualTreeHelper.GetParent(_item)
32.             EndGet
33.         EndProperty
34.     EndClass
35.     ”’ <summary>
36.     ”’ Defines an interface that must be implemented to generate the LinqToTree methods
37.     ”’ </summary>
38.     ”’ <typeparam name="T"></typeparam>
39.     PublicInterface ILinqTree(Of T)
40.         Function Children() As IEnumerable(OfT)
41.  
42.         ReadOnlyProperty Parent() As T
43.     EndInterface
44.  
45.     ”’ <summary>
46.     ”’ Returns a collection of descendant elements.
47.     ”’ </summary>
48.     <Extension()>
49.     PublicFunction Descendants(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
50.         Dim adapter As ILinqTree(OfDependencyObject) = NewVisualTreeAdapter(item)
51.         Dim list As New List(OfDependencyObject)
52.         ForEach child In adapter.Children()
53.             list.Add(child)
54.             Dim ad2 As ILinqTree(OfDependencyObject) = NewVisualTreeAdapter(child)
55.             ForEach grandChild In child.Descendants()
56.  
57.  
58.                 list.Add(grandChild)
59.             Next
60.         Next
61.         Return list
62.     EndFunction
63.  
64.     ”’ <summary>
65.     ”’ Returns a collection containing this element and all descendant elements.
66.     ”’ </summary>
67.     <Extension()>
68.     PublicFunction DescendantsAndSelf(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
69.         Dim list As New List(OfDependencyObject)
70.         list.Add(item)
71.         ForEach child In item.Descendants()
72.             list.Add(child)
73.         Next
74.         Return list
75.     EndFunction
76.  
77.     ”’ <summary>
78.     ”’ Returns a collection of ancestor elements.
79.     ”’ </summary>
80.     <Extension()>
81.     PublicFunction Ancestors(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
82.         Dim adapter As ILinqTree(OfDependencyObject) = NewVisualTreeAdapter(item)
83.         Dim list As New List(OfDependencyObject)
84.  
85.         Dim parent = adapter.Parent
86.         While parent IsNot Nothing
87.             list.Add(parent)
88.             adapter = New VisualTreeAdapter(parent)
89.             parent = adapter.Parent
90.         EndWhile
91.         Return list
92.     EndFunction
93.  
94.     ”’ <summary>
95.     ”’ Returns a collection containing this element and all ancestor elements.
96.     ”’ </summary>
97.     <Extension()>
98.     PublicFunction AncestorsAndSelf(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
99.         Dim list As New List(OfDependencyObject)
100.         list.Add(item)
101.  
102.         ForEach ancestor In item.Ancestors()
103.             list.Add(ancestor)
104.         Next
105.         Return list
106.     EndFunction
107.  
108.     ”’ <summary>
109.     ”’ Returns a collection of child elements.
110.     ”’ </summary>
111.     <Extension()>
112.     PublicFunction Elements(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
113.         Dim list As New List(OfDependencyObject)
114.         Dim adapter As ILinqTree(OfDependencyObject) = NewVisualTreeAdapter(item)
115.         ForEach child In adapter.Children()
116.             list.Add(child)
117.         Next
118.         Return list
119.     EndFunction
120.  
121.     ”’ <summary>
122.     ”’ Returns a collection of the sibling elements before this node, in document order.    ”’ </summary>
123.     <Extension()>
124.     PublicFunction ElementsBeforeSelf(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
125.         Dim list As New List(OfDependencyObject)
126.         If item.Ancestors().FirstOrDefault() Is NothingThen
127.             ‘yield Exit Function
128.             ‘Exit Function
129.             Return list
130.         EndIf
131.         ForEach child In item.Ancestors().First().Elements()
132.             If child.Equals(item) Then
133.                 Exit For
134.             EndIf
135.             list.Add(child)
136.         Next
137.         Return list
138.     EndFunction
139.  
140.     ”’ <summary>
141.     ”’ Returns a collection of the after elements after this node, in document order.
142.     ”’ </summary>
143.     <Extension()>
144.     PublicFunction ElementsAfterSelf(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
145.         Dim list As New List(OfDependencyObject)
146.         If item.Ancestors().FirstOrDefault() Is NothingThen
147.             ‘yield Exit Function
148.             Return list
149.             ‘Exit Function
150.         EndIf
151.         DimafterSelf As Boolean = False
152.         ForEach child In item.Ancestors().First().Elements()
153.             IfafterSelf Then
154.                 ‘yield Return child
155.                 list.Add(child)
156.             EndIf
157.  
158.             If child.Equals(item) Then
159.                 afterSelf = True
160.             EndIf
161.         Next
162.         Return list
163.     EndFunction
164.  
165.     ”’ <summary>
166.     ”’ Returns a collection containing this element and all child elements.
167.     ”’ </summary>
168.     <Extension()>
169.     PublicFunction ElementsAndSelf(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
170.         Dim list As New List(OfDependencyObject)
171.         ‘yield Return item
172.         list.Add(item)
173.  
174.         ForEach child In item.Elements()
175.             ‘yield Return child
176.             list.Add(child)
177.         Next
178.         Return list
179.     EndFunction
180.  
181.     ”’ <summary>
182.     ”’ Returns a collection of descendant elements which match the given type.
183.     ”’ </summary>
184.     <Extension()>
185.     PublicFunction Descendants(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
186.         Return item.Descendants().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
187.     EndFunction
188.  
189.  
190.  
191.     ”’ <summary>
192.     ”’ Returns a collection of the sibling elements before this node, in document order
193.     ”’ which match the given type.
194.     ”’ </summary>
195.     <Extension()>
196.     PublicFunction ElementsBeforeSelf(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
197.         Return item.ElementsBeforeSelf().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
198.     EndFunction
199.  
200.     ”’ <summary>
201.     ”’ Returns a collection of the after elements after this node, in document order
202.     ”’ which match the given type.
203.     ”’ </summary>
204.     <Extension()>
205.     PublicFunction ElementsAfterSelf(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
206.         Return item.ElementsAfterSelf().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
207.     EndFunction
208.  
209.     ”’ <summary>
210.     ”’ Returns a collection containing this element and all descendant elements
211.     ”’ which match the given type.
212.     ”’ </summary>
213.     <Extension()>
214.     PublicFunction DescendantsAndSelf(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
215.         Return item.DescendantsAndSelf().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
216.     EndFunction
217.  
218.     ”’ <summary>
219.     ”’ Returns a collection of ancestor elements which match the given type.
220.     ”’ </summary>
221.     <Extension()>
222.     PublicFunction Ancestors(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
223.         Return item.Ancestors().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
224.     EndFunction
225.  
226.     ”’ <summary>
227.     ”’ Returns a collection containing this element and all ancestor elements
228.     ”’ which match the given type.
229.     ”’ </summary>
230.     <Extension()>
231.     PublicFunction AncestorsAndSelf(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
232.         Return item.AncestorsAndSelf().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
233.     EndFunction
234.  
235.     ”’ <summary>
236.     ”’ Returns a collection of child elements which match the given type.
237.     ”’ </summary>
238.     ”’
239.     <Extension()>
240.     PublicFunction Elements(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
241.         Return item.Elements().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
242.     EndFunction
243.  
244.     ”’ <summary>
245.     ”’ Returns a collection containing this element and all child elements.
246.     ”’ which match the given type.
247.     ”’ </summary>
248.     <Extension()>
249.     PublicFunction ElementsAndSelf(Of T)(item AsDependencyObject) AsIEnumerable(OfDependencyObject)
250.         Return item.ElementsAndSelf().Where(Function(i) TypeOf i Is T).Cast(OfDependencyObject)()
251.     EndFunction
252.  
253.  
254.     ”’ <summary>
255.     ”’ Applies the given function to each of the items in the supplied
256.     ”’ IEnumerable.
257.     ”’ </summary>
258.     <Extension()>
259.     PrivateFunction DrillDown(items AsIEnumerable(Of DependencyObject), [function] As Func(OfDependencyObject, IEnumerable(OfDependencyObject))) AsIEnumerable(OfDependencyObject)
260.         Dim list As New List(OfDependencyObject)
261.         ForEach item In items
262.             ForEach itemChild In [function](item)
263.                 ‘yield Return itemChild
264.                 list.Add(itemChild)
265.             Next
266.         Next
267.         Return list
268.     EndFunction
269.  
270.  
271.     ”’ <summary>
272.     ”’ Applies the given function to each of the items in the supplied
273.     ”’ IEnumerable, which match the given type.
274.     ”’ </summary>
275.     <Extension()>
276.     PublicFunction DrillDown(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject), [function] As Func(OfDependencyObject, IEnumerable(OfDependencyObject))) AsIEnumerable(OfDependencyObject)
277.         Dim list As New List(OfDependencyObject)
278.         ForEach item In items
279.             ForEach itemChild In [function](item)
280.                 IfTypeOf itemChild Is T Then
281.                     ‘yield Return DirectCast(itemChild, T)
282.                     list.Add(DirectCast(itemChild, T))
283.                 EndIf
284.             Next
285.         Next
286.         Return list
287.     EndFunction
288.  
289.  
290.     ”’ <summary>
291.     ”’ Returns a collection of descendant elements.
292.     ”’ </summary>
293.     <Extension()>
294.     PublicFunction Descendants(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
295.  
296.         Return items.DrillDown(Function(i) i.Descendants())
297.     EndFunction
298.  
299.     ”’ <summary>
300.     ”’ Returns a collection containing this element and all descendant elements.
301.     ”’ </summary>
302.     <Extension()>
303.     PublicFunction DescendantsAndSelf(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
304.         Return items.DrillDown(Function(i) i.DescendantsAndSelf())
305.     EndFunction
306.  
307.     ”’ <summary>
308.     ”’ Returns a collection of ancestor elements.
309.     ”’ </summary>
310.     <Extension()>
311.     PublicFunction Ancestors(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
312.         Return items.DrillDown(Function(i) i.Ancestors())
313.     EndFunction
314.  
315.     ”’ <summary>
316.     ”’ Returns a collection containing this element and all ancestor elements.
317.     ”’ </summary>
318.     <Extension()>
319.     PublicFunction AncestorsAndSelf(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
320.         Return items.DrillDown(Function(i) i.AncestorsAndSelf())
321.     EndFunction
322.  
323.     ”’ <summary>
324.     ”’ Returns a collection of child elements.
325.     ”’ </summary>
326.     <Extension()>
327.     PublicFunction Elements(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
328.         Return items.DrillDown(Function(i) i.Elements())
329.     EndFunction
330.  
331.     ”’ <summary>
332.     ”’ Returns a collection containing this element and all child elements.
333.     ”’ </summary>
334.     <Extension()>
335.     PublicFunction ElementsAndSelf(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
336.         Return items.DrillDown(Function(i) i.ElementsAndSelf())
337.     EndFunction
338.  
339.  
340.     ”’ <summary>
341.     ”’ Returns a collection of descendant elements which match the given type.
342.     ”’ </summary>
343.     <Extension()>
344.     PublicFunction Descendants(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
345.         Return items.DrillDown(Of T)(Function(i) i.Descendants())
346.     EndFunction
347.  
348.     ”’ <summary>
349.     ”’ Returns a collection containing this element and all descendant elements.
350.     ”’ which match the given type.
351.     ”’ </summary>
352.     <Extension()>
353.     PublicFunction DescendantsAndSelf(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
354.         Return items.DrillDown(Of T)(Function(i) i.DescendantsAndSelf())
355.     EndFunction
356.  
357.     ”’ <summary>
358.     ”’ Returns a collection of ancestor elements which match the given type.
359.     ”’ </summary>
360.     <Extension()>
361.     PublicFunction Ancestors(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
362.         Return items.DrillDown(Of T)(Function(i) i.Ancestors())
363.     EndFunction
364.  
365.     ”’ <summary>
366.     ”’ Returns a collection containing this element and all ancestor elements.
367.     ”’ which match the given type.
368.     ”’ </summary>
369.     <Extension()>
370.     PublicFunction AncestorsAndSelf(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
371.         Return items.DrillDown(Of T)(Function(i) i.AncestorsAndSelf())
372.     EndFunction
373.  
374.     ”’ <summary>
375.     ”’ Returns a collection of child elements which match the given type.
376.     ”’ </summary>
377.     <Extension()>
378.     PublicFunction Elements(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
379.         Return items.DrillDown(Of T)(Function(i) i.Elements())
380.     EndFunction
381.  
382.     ”’ <summary>
383.     ”’ Returns a collection containing this element and all child elements.
384.     ”’ which match the given type.
385.     ”’ </summary>
386.     <Extension()>
387.     PublicFunction ElementsAndSelf(Of T AsDependencyObject)(items AsIEnumerable(Of DependencyObject)) As IEnumerable(OfDependencyObject)
388.         Return items.DrillDown(Of T)(Function(i) i.ElementsAndSelf())
389.     EndFunction
390.  
391.  
392.     ‘End Namespace
393. End Module

Now, in your codebehind for XAML pages that use the WebBrowser control where you wish to suppress pinch or scroll, add the following declaration:

1. Dim WithEvents MBH As WebBrowserHelper

 

Finally, in Public Sub New () of your codebehind of these XAML pages, associate this declared WebBrowserHelper with an actual WebBrowser (in this case named “MyWebBrowser”):

1. MBH = New WebBrowserHelper(MyWebBrowser)

 

That’s it!

Adapted from C# to VB, and for completeness and accuracy, from:

1. Suppressing Zoom and Scroll interactions in the Windows Phone 7 WebBrowser Control

   http://www.scottlogic.co.uk/blog/colin/2011/11/suppressing-zoom-and-scroll-interactions-in-the-windows-phone-7-browser-control/

Daily Gem: VB / Silverlight / WP7.5 – Infinite scrolling lists

How to raise an end-of-list reached event so you can add more items.

Step 1:  Subclass the standard Listbox with the following code

Code Snippet

1. Imports System.Windows.Controls.Primitives
2.  
3. Public ClassExtendedListBox
4.     InheritsListBox
5.  
6.     Protected _isBouncy As Boolean = False
7.     PrivatealreadyHookedScrollEvents As Boolean = False
8.  
9.     PublicSub New()
10.         AddHandlerMe.Loaded, NewRoutedEventHandler(AddressOfListBox_Loaded)
11.     EndSub
12.  
13.     PrivateSub ListBox_Loaded(sender As Object, e As RoutedEventArgs)
14.         Dimsb As ScrollBar = Nothing
15.         Dimsv As ScrollViewer = Nothing
16.         IfalreadyHookedScrollEvents Then
17.             Return
18.         EndIf
19.  
20.         alreadyHookedScrollEvents = True
21.         Me.[AddHandler](ExtendedListBox.ManipulationCompletedEvent, DirectCast(AddressOf LB_ManipulationCompleted, EventHandler(OfManipulationCompletedEventArgs)), True)
22.         sb = DirectCast(FindElementRecursive(Me, GetType(ScrollBar)), ScrollBar)
23.         sv = DirectCast(FindElementRecursive(Me, GetType(ScrollViewer)), ScrollViewer)
24.  
25.         Ifsv IsNot Nothing Then
26.             ‘ Visual States are always on the first child of the control template
27.             Dim element As FrameworkElement = TryCast(VisualTreeHelper.GetChild(sv, 0), FrameworkElement)
28.             If element IsNot Nothing Then
29.                 Dimvgroup As VisualStateGroup = FindVisualState(element, "VerticalCompression")
30.                 Dimhgroup As VisualStateGroup = FindVisualState(element, "HorizontalCompression")
31.                 Ifvgroup IsNot Nothing Then
32.                     AddHandlervgroup.CurrentStateChanging, NewEventHandler(OfVisualStateChangedEventArgs)(AddressOfvgroup_CurrentStateChanging)
33.                 EndIf
34.                 Ifhgroup IsNot Nothing Then
35.                     AddHandlerhgroup.CurrentStateChanging, NewEventHandler(OfVisualStateChangedEventArgs)(AddressOfhgroup_CurrentStateChanging)
36.                 EndIf
37.             EndIf
38.         EndIf
39.  
40.     EndSub
41.  
42.     PublicDelegate Sub OnCompression(sender As Object, e AsCompressionEventArgs)
43.     PublicEvent Compression As OnCompression
44.  
45.     PrivateSub hgroup_CurrentStateChanging(sender AsObject, e AsVisualStateChangedEventArgs)
46.         If e.NewState.Name = "CompressionLeft" Then
47.             _isBouncy = True
48.             RaiseEvent Compression(Me, NewCompressionEventArgs(CompressionType.Left))
49.         EndIf
50.  
51.         If e.NewState.Name = "CompressionRight" Then
52.             _isBouncy = True
53.             RaiseEvent Compression(Me, NewCompressionEventArgs(CompressionType.Right))
54.         EndIf
55.         If e.NewState.Name = "NoHorizontalCompression" Then
56.             _isBouncy = False
57.         EndIf
58.     EndSub
59.  
60.     PrivateSub vgroup_CurrentStateChanging(sender AsObject, e AsVisualStateChangedEventArgs)
61.         If e.NewState.Name = "CompressionTop" Then
62.             _isBouncy = True
63.             RaiseEvent Compression(Me, NewCompressionEventArgs(CompressionType.Top))
64.         EndIf
65.         If e.NewState.Name = "CompressionBottom" Then
66.             _isBouncy = True
67.             RaiseEvent Compression(Me, NewCompressionEventArgs(CompressionType.Bottom))
68.         EndIf
69.         If e.NewState.Name = "NoVerticalCompression" Then
70.             _isBouncy = False
71.         EndIf
72.     EndSub
73.  
74.     PrivateSub LB_ManipulationCompleted(sender AsObject, e AsManipulationCompletedEventArgs)
75.         If _isBouncy Then
76.             _isBouncy = False
77.         EndIf
78.     EndSub
79.  
80.     PrivateFunction FindElementRecursive(parent AsFrameworkElement, targetType As Type) As UIElement
81.         DimchildCount As Integer = VisualTreeHelper.GetChildrenCount(parent)
82.         DimreturnElement As UIElement = Nothing
83.         IfchildCount > 0 Then
84.             For i As Integer = 0 To childCount – 1
85.                 Dim element As [Object] = VisualTreeHelper.GetChild(parent, i)
86.                 ‘If element.[GetType]() = targetType Then
87.                 ‘If element.GetType.FullName = targetType.FullName Then
88.                 If element.GetType.Equals(targetType) Then
89.  
90.                     ReturnTryCast(element, UIElement)
91.                 Else
92.                     returnElement = FindElementRecursive(TryCast(VisualTreeHelper.GetChild(parent, i), FrameworkElement), targetType)
93.                 EndIf
94.             Next
95.         EndIf
96.         ReturnreturnElement
97.     EndFunction
98.  
99.     PrivateFunction FindVisualState(element AsFrameworkElement, name As String) As VisualStateGroup
100.         If element Is Nothing Then
101.             ReturnNothing
102.         EndIf
103.  
104.         Dim groups As IList(OfVisualStateGroup) = VisualStateManager.GetVisualStateGroups(element)
105.         ForEach group As VisualStateGroupIn groups
106.             If group.Name = name Then
107.                 Return group
108.             EndIf
109.         Next
110.  
111.         ReturnNothing
112.     EndFunction
113. End Class
114.  
115. Public ClassCompressionEventArgs
116.     InheritsEventArgs
117.     PublicProperty Type() As CompressionType
118.         Get
119.             Return m_Type
120.         EndGet
121.         ProtectedSet(value AsCompressionType)
122.             m_Type = value
123.         EndSet
124.     EndProperty
125.     Private m_Type As CompressionType
126.  
127.     PublicSub New(type__1 AsCompressionType)
128.         Type = type__1
129.     EndSub
130. End Class
131.  
132. Public EnumCompressionType
133.     Top
134.     Bottom
135.     Left
136.     Right
137. End Enum

 

Step 2:  Add the following XAML to the Application.Resources section of App.xaml

XAML Snippet

1. <StyleTargetType="ScrollViewer">
2.     <Setter Property="VerticalScrollBarVisibility" Value="Auto"/>
3.     <Setter Property="HorizontalScrollBarVisibility" Value="Auto"/>
4.     <Setter Property="Background" Value="Transparent"/>
5.     <Setter Property="Padding" Value="0"/>
6.     <Setter Property="BorderThickness" Value="0"/>
7.     <Setter Property="BorderBrush" Value="Transparent"/>
8.     <Setter Property="Template">
9.         <Setter.Value>
10.             <ControlTemplateTargetType="ScrollViewer">
11.                 <BorderBorderBrush="{TemplateBindingBorderBrush}"BorderThickness="{TemplateBindingBorderThickness}" Background="{TemplateBinding Background}">
12.                     <VisualStateManager.VisualStateGroups>
13.                         <VisualStateGroup x:Name="ScrollStates">
14.                             <VisualStateGroup.Transitions>
15.                                 <VisualTransitionGeneratedDuration="00:00:00.5"/>
16.                             </VisualStateGroup.Transitions>
17.                             <VisualState x:Name="Scrolling">
18.                                 <Storyboard>
19.                                     <DoubleAnimation Storyboard.TargetName="VerticalScrollBar" Storyboard.TargetProperty="Opacity" To="1" Duration="0"/>
20.                                     <DoubleAnimation Storyboard.TargetName="HorizontalScrollBar" Storyboard.TargetProperty="Opacity" To="1" Duration="0"/>
21.                                 </Storyboard>
22.                             </VisualState>
23.                             <VisualState x:Name="NotScrolling"/>
24.                         </VisualStateGroup>
25.                         <VisualStateGroup x:Name="VerticalCompression">
26.                             <VisualState x:Name="NoVerticalCompression"/>
27.                             <VisualState x:Name="CompressionTop"/>
28.                             <VisualState x:Name="CompressionBottom"/>
29.                         </VisualStateGroup>
30.                         <VisualStateGroup x:Name="HorizontalCompression">
31.                             <VisualState x:Name="NoHorizontalCompression"/>
32.                             <VisualState x:Name="CompressionLeft"/>
33.                             <VisualState x:Name="CompressionRight"/>
34.                         </VisualStateGroup>
35.                     </VisualStateManager.VisualStateGroups>
36.  
37.  
38.                     <Grid Margin="{TemplateBinding Padding}">
39.                         <ScrollContentPresenter x:Name="ScrollContentPresenter" Content="{TemplateBinding Content}"ContentTemplate="{TemplateBindingContentTemplate}"/>
40.                         <ScrollBar x:Name="VerticalScrollBar"IsHitTestVisible="False" Height="Auto" Width="5"HorizontalAlignment="Right"VerticalAlignment="Stretch" Visibility="{TemplateBindingComputedVerticalScrollBarVisibility}"IsTabStop="False" Maximum="{TemplateBindingScrollableHeight}" Minimum="0" Value="{TemplateBindingVerticalOffset}" Orientation="Vertical"ViewportSize="{TemplateBindingViewportHeight}" />
41.                         <ScrollBar x:Name="HorizontalScrollBar"IsHitTestVisible="False" Width="Auto" Height="5"HorizontalAlignment="Stretch"VerticalAlignment="Bottom" Visibility="{TemplateBindingComputedHorizontalScrollBarVisibility}"IsTabStop="False" Maximum="{TemplateBindingScrollableWidth}" Minimum="0" Value="{TemplateBindingHorizontalOffset}" Orientation="Horizontal"ViewportSize="{TemplateBindingViewportWidth}" />
42.                     </Grid>
43.                 </Border>
44.             </ControlTemplate>
45.         </Setter.Value>
46.     </Setter>
47. </Style>

You can now simply replace your ListBox references with ExtendedListBox references in your code wherever a listbox is used.

1. <local:ExtendedListBox x:Name="lbMyList"VerticalAlignment="Top"ItemsSource="{Binding}">

 

You might handle list-end / top scroll events in your code-behind as follows:

Code Snippet

1. Private SublbMyList_Compression(sender As Object, e As CompressionEventArgs) HandleslbMyList.Compression
2.     DimCompressionArgs = CType(e, CompressionEventArgs)
3.     SelectCase CompressionArgs.Type
4.         CaseCompressionType.Bottom ‘Bottom reached… add more list items
5.             …
6.         CaseCompressionType.Top ‘At top  fetch and add earlier list items
7.             …
8.     EndSelect
9. End Sub

Cheers. 

---

Adapted from C# to VB, and for completeness and accuracy, from: 

1. Windows Phone Mango change, Listbox: How to detect compression(end of scroll) states ?http://blogs.msdn.com/b/slmperf/archive/2011/06/30/windows-phone-mango-change-listbox-how-to-detect-compression-end-of-scroll-states.aspx
   
2. ExtendedListBox: custom WP7 Listbox control which detects end of scroll, allows infinite scrolling
   http://nuncaalaprimera.com/2012/01/extendedlistbox-custom-wp7-listbox-control-which-detects-end-of-scroll-allows-infinite-scrolling/

Daily Gem: Quickly and temporarily bypass Vista / Win 7 file redirection in your VB6 Apps

How to quickly get around redirection in your VB6 app:

a) You wish to check for or launch program in “c:\Windows\System” folder (Without redirection to “c:\Windows\SysWow64”)

Use the “\SysNative” path!

Public Const CSIDL_WINDOWS = &H24
GetSpecialFolder(CSIDL_WINDOWS) & "\SysNative\"
Note, the GetSpecialFolder function appears in many other plaes, like this.

For example:

z = shell(GetSpecialFolder(CSIDL_WINDOWS) & "\SysNative\<64-bit appname>.exe")

b) Check for program in “c:\Program Files” without redirection to “c:\Program Files (x86)”

Abuse the “\SysNative” path!

GetSpecialFolder(CSIDL_WINDOWS) & "\SysNative\..\..\Program Files\"

For example:

z = shell(GetSpecialFolder(CSIDL_WINDOWS) & "\SysNative\..\..\Program Files\<64-bit appname>.exe")

This leads to the question, how to get “Program Files” directory name?

Answer:

ProgramFilesFolder$ = Environ("ProgramW6432")
ProgramFilesFolder$ = Mid(ProgramFilesFolder$, InStr(ProgramFilesFolder$, "\") + 1)
z = shell(GetSpecialFolder(&H24) & "\SysNative\..\.." & ProgramFilesFolder$ & "\<64-bit appname>.exe")