UIElementCollection.IndexOf(UIElement) Method

Definition

Namespace:

System.Windows.Controls

Assembly:

PresentationFramework.dll

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

public:
 virtual int IndexOf(System::Windows::UIElement ^ element);

public virtual int IndexOf (System.Windows.UIElement element);

abstract member IndexOf : System.Windows.UIElement -> int
override this.IndexOf : System.Windows.UIElement -> int

Public Overridable Function IndexOf (element As UIElement) As Integer

Parameters

element

UIElement

The element whose index position is required.

Returns

Int32

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

Examples

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>

...

private int c_counter = 0;
void FindIndex(object sender, RoutedEventArgs e)
{
    c_counter+=1;
    // Create a new Text element.
    TextBlock newText = new TextBlock();
    // 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 #" + 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);
}

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