Dario Sassi
250 lines
9.4 KiB
VB.net
250 lines
9.4 KiB
VB.net
' Follow steps 1a or 1b and then 2 to use this custom control in a XAML file.
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'
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' Step 1a) Using this custom control in a XAML file that exists in the current project.
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' Add this XmlNamespace attribute to the root element of the markup file where it is
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' to be used:
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'
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' xmlns:MyNamespace="clr-namespace:EgtWPFLib5"
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'
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'
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' Step 1b) Using this custom control in a XAML file that exists in a different project.
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' Add this XmlNamespace attribute to the root element of the markup file where it is
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' to be used:
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'
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' xmlns:MyNamespace="clr-namespace:EgtWPFLib5;assembly=EgtWPFLib5"
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'
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' You will also need to add a project reference from the project where the XAML file lives
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' to this project and Rebuild to avoid compilation errors:
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'
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' Right click on the target project in the Solution Explorer and
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' "Add Reference"->"Projects"->[Browse to and select this project]
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'
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'
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' Step 2)
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' Go ahead and use your control in the XAML file. Note that Intellisense in the
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' XML editor does not currently work on custom controls and its child elements.
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'
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' <MyNamespace:EgtTabControl/>
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'
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Imports System.Windows.Controls.Primitives
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Imports System.Collections.Specialized
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Imports System.Windows.Threading
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' Extended TabControl which saves the displayed item so you don't get the performance hit of
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' unloading and reloading the VisualTree when switching tabs
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' Made some modifications so it reuses a TabItem's ContentPresenter when doing drag/drop operations
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<TemplatePart(Name:="PART_ItemsHolder", Type:=GetType(Panel))> _
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Public Class EgtTabControl
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Inherits System.Windows.Controls.TabControl
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' Holds all items, but only marks the current tab's item as visible
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Private _itemsHolder As Panel = Nothing
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' Temporaily holds deleted item in case this was a drag/drop operation
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Private _deletedObject As Object = Nothing
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Public Sub New()
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MyBase.New()
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' this is necessary so that we get the initial databound selected item
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AddHandler Me.ItemContainerGenerator.StatusChanged, AddressOf ItemContainerGenerator_StatusChanged
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End Sub
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''' <summary>
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''' if containers are done, generate the selected item
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''' </summary>
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''' <param name="sender"></param>
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''' <param name="e"></param>
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Private Sub ItemContainerGenerator_StatusChanged(sender As Object, e As EventArgs)
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If Me.ItemContainerGenerator.Status = GeneratorStatus.ContainersGenerated Then
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RemoveHandler Me.ItemContainerGenerator.StatusChanged, AddressOf ItemContainerGenerator_StatusChanged
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UpdateSelectedItem()
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End If
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End Sub
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''' <summary>
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''' get the ItemsHolder and generate any children
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''' </summary>
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Public Overrides Sub OnApplyTemplate()
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MyBase.OnApplyTemplate()
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_itemsHolder = TryCast(MyBase.GetTemplateChild("PART_ItemsHolder"), Panel)
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UpdateSelectedItem()
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End Sub
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''' <summary>
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''' when the items change we remove any generated panel children and add any new ones as necessary
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''' </summary>
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''' <param name="e"></param>
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Protected Overrides Sub OnItemsChanged(e As NotifyCollectionChangedEventArgs)
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MyBase.OnItemsChanged(e)
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If _itemsHolder Is Nothing Then
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Return
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End If
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Select Case e.Action
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Case NotifyCollectionChangedAction.Reset
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_itemsHolder.Children.Clear()
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If MyBase.Items.Count > 0 Then
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MyBase.SelectedItem = MyBase.Items(0)
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UpdateSelectedItem()
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End If
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Exit Select
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Case NotifyCollectionChangedAction.Add, NotifyCollectionChangedAction.Remove
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' Search for recently deleted items caused by a Drag/Drop operation
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If e.NewItems IsNot Nothing AndAlso _deletedObject IsNot Nothing Then
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For Each item As Object In e.NewItems
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If _deletedObject Is item Then
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' If the new item is the same as the recently deleted one (i.e. a drag/drop event)
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' then cancel the deletion and reuse the ContentPresenter so it doesn't have to be
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' redrawn. We do need to link the presenter to the new item though (using the Tag)
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Dim cp As ContentPresenter = FindChildContentPresenter(_deletedObject)
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If cp IsNot Nothing Then
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Dim index As Integer = _itemsHolder.Children.IndexOf(cp)
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TryCast(_itemsHolder.Children(index), ContentPresenter).Tag = If((TypeOf item Is TabItem), item, (Me.ItemContainerGenerator.ContainerFromItem(item)))
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End If
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_deletedObject = Nothing
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End If
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Next
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End If
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If e.OldItems IsNot Nothing Then
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For Each item As Object In e.OldItems
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_deletedObject = item
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' We want to run this at a slightly later priority in case this
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' is a drag/drop operation so that we can reuse the template
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Me.Dispatcher.BeginInvoke(DispatcherPriority.DataBind, (Sub()
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If _deletedObject IsNot Nothing Then
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Dim cp As ContentPresenter = FindChildContentPresenter(_deletedObject)
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If cp IsNot Nothing Then
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Me._itemsHolder.Children.Remove(cp)
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End If
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End If
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End Sub))
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Next
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End If
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UpdateSelectedItem()
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Exit Select
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Case NotifyCollectionChangedAction.Replace
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Throw New NotImplementedException("Replace not implemented yet")
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End Select
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End Sub
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''' <summary>
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''' update the visible child in the ItemsHolder
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''' </summary>
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''' <param name="e"></param>
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Protected Overrides Sub OnSelectionChanged(e As SelectionChangedEventArgs)
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MyBase.OnSelectionChanged(e)
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UpdateSelectedItem()
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End Sub
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''' <summary>
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''' generate a ContentPresenter for the selected item
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''' </summary>
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Private Sub UpdateSelectedItem()
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If _itemsHolder Is Nothing Then
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Return
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End If
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' generate a ContentPresenter if necessary
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Dim item As TabItem = GetSelectedTabItem()
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If item IsNot Nothing Then
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CreateChildContentPresenter(item)
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End If
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' show the right child
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For Each child As ContentPresenter In _itemsHolder.Children
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child.Visibility = If((TryCast(child.Tag, TabItem).IsSelected), Visibility.Visible, Visibility.Collapsed)
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Next
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End Sub
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''' <summary>
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''' create the child ContentPresenter for the given item (could be data or a TabItem)
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''' </summary>
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''' <param name="item"></param>
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''' <returns></returns>
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Private Function CreateChildContentPresenter(item As Object) As ContentPresenter
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If item Is Nothing Then
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Return Nothing
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End If
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Dim cp As ContentPresenter = FindChildContentPresenter(item)
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If cp IsNot Nothing Then
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Return cp
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End If
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' the actual child to be added. cp.Tag is a reference to the TabItem
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cp = New ContentPresenter() With {
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.Content = If((TypeOf item Is TabItem), TryCast(item, TabItem).Content, item),
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.ContentTemplate = Me.SelectedContentTemplate,
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.ContentTemplateSelector = Me.SelectedContentTemplateSelector,
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.ContentStringFormat = Me.SelectedContentStringFormat,
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.Visibility = Visibility.Collapsed,
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.Tag = If((TypeOf item Is TabItem), item, (Me.ItemContainerGenerator.ContainerFromItem(item)))
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}
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_itemsHolder.Children.Add(cp)
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Return cp
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End Function
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''' <summary>
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''' Find the CP for the given object. data could be a TabItem or a piece of data
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''' </summary>
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''' <param name="data"></param>
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''' <returns></returns>
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Private Function FindChildContentPresenter(data As Object) As ContentPresenter
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If TypeOf data Is TabItem Then
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data = TryCast(data, TabItem).Content
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End If
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If data Is Nothing Then
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Return Nothing
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End If
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If _itemsHolder Is Nothing Then
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Return Nothing
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End If
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For Each cp As ContentPresenter In _itemsHolder.Children
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If cp.Content Is data Then
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Return cp
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End If
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Next
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Return Nothing
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End Function
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''' <summary>
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''' copied from TabControl; wish it were protected in that class instead of private
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''' </summary>
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''' <returns></returns>
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Protected Function GetSelectedTabItem() As TabItem
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Dim selectedItem As Object = MyBase.SelectedItem
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If selectedItem Is Nothing Then
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Return Nothing
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End If
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If _deletedObject Is selectedItem Then
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End If
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Dim item As TabItem = TryCast(selectedItem, TabItem)
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If item Is Nothing Then
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item = TryCast(MyBase.ItemContainerGenerator.ContainerFromIndex(MyBase.SelectedIndex), TabItem)
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End If
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Return item
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End Function
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End Class |