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UIElementCollection.IndexOf Method (UIElement)

 

Returns the index position of a specified element in a UIElementCollection.

Namespace:   System.Windows.Controls
Assembly:  PresentationFramework (in PresentationFramework.dll)

Public Overridable Function IndexOf (
	element As UIElement
) As Integer

Parameters

element
Type: System.Windows.UIElement

The element whose index position is required.

Return Value

Type: System.Int32

The index position of the element. -1 if the element is not in the collection.

The following example finds the index position of a UIElement within a UIElementCollection.

<DockPanel Name="ParentElement">

    <TextBlock DockPanel.Dock="Top" Name="TxtDisplay"></TextBlock>

    <Button DockPanel.Dock="Top" Click="FindIndex">What is the Index Number
        of the Element Just Added?</Button>
    <DockPanel Name="MainDisplayPanel">
        <TextBlock DockPanel.Dock="Top">Text 1</TextBlock>
        <TextBlock DockPanel.Dock="Top">Text 2</TextBlock>
    </DockPanel>
</DockPanel>

...

Dim c_counter as Integer = 0
   Private Sub FindIndex(ByVal sender As Object, ByVal args As RoutedEventArgs)
       Try
           Dim newText As TextBlock = New TextBlock()
           c_counter = c_counter + 1
           ' Add this element to the UIElementCollection of the DockPanel element.
           MainDisplayPanel.Children.Add(newText)
           ' Add a text node under the Text element. This text is displayed. 
           newText.Text = "New element #" & CStr(c_counter)
           DockPanel.SetDock(newText, Dock.Top)
           ' Display the Index number of the new element.    
           TxtDisplay.Text = "The Index of the new element is " & MainDisplayPanel.Children.IndexOf(newText)
       Catch ex As System.Exception
           System.Windows.MessageBox.Show(ex.Message)
       End Try
   End Sub

.NET Framework
Available since 3.0
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