Invoke a Control Using UI Automation

 
System_CAPS_noteNote

This documentation is intended for .NET Framework developers who want to use the managed UI Automation classes defined in the System.Windows.Automation namespace. For the latest information about UI Automation, see Windows Automation API: UI Automation.

This topic demonstrates how to perform the following tasks:

  • Find a control that matches specific property conditions by walking the control view of the UI Automation tree for the target application.

  • Create an AutomationElement for each control.

  • Obtain an InvokePattern object from any UI Automation element found that supports the InvokePattern control pattern.

  • Use Invoke to invoke the control from a client event handler.

Example

This example uses the TryGetCurrentPattern method of the AutomationElement class to generate an InvokePattern object and invoke a control by using the Invoke method.

'''--------------------------------------------------------------------
''' <summary>
''' Walks the UI Automation tree of the target and reports the control 
''' type of each element it finds in the control view to the client.
''' </summary>
''' <param name="targetTreeViewElement">
''' The root of the search on this iteration.
''' </param>
''' <param name="treeviewIndex">
''' The TreeView index for this iteration.
''' </param>
''' <remarks>
''' This is a recursive function that maps out the structure of the 
''' subtree beginning at the AutomationElement passed in as 
''' rootElement on the first call. This could be, for example,
''' an application window.
''' CAUTION: Do not pass in AutomationElement.RootElement. Attempting 
''' to map out the entire subtree of the desktop could take a very 
''' long time and even lead to a stack overflow.
''' </remarks>
'''--------------------------------------------------------------------
Private Sub FindTreeViewDescendants( _
ByVal targetTreeViewElement As AutomationElement, _
ByVal treeviewIndex As Integer)
    If (IsNothing(targetTreeViewElement)) Then
        Return
    End If

    Dim elementNode As AutomationElement = _
    TreeWalker.ControlViewWalker.GetFirstChild(targetTreeViewElement)

    While Not (elementNode Is Nothing)
        Dim elementInfo As New Label()
        elementInfo.Margin = New Thickness(0)
        clientTreeViews(treeviewIndex).Children.Add(elementInfo)

        ' Compile information about the control.
        elementInfoCompile = New StringBuilder()
        Dim controlName As String
        If (elementNode.Current.Name = "") Then
            controlName = "Unnamed control"
        Else
            controlName = elementNode.Current.Name
        End If
        Dim autoIdName As String
        If (elementNode.Current.AutomationId = "") Then
            autoIdName = "No AutomationID"
        Else
            autoIdName = elementNode.Current.AutomationId
        End If


        elementInfoCompile.Append(controlName).Append(" (") _
        .Append(elementNode.Current.ControlType.LocalizedControlType) _
        .Append(" - ").Append(autoIdName).Append(")")

        ' Test for the control patterns of interest for this sample.
        Dim objPattern As Object = Nothing
        Dim expcolPattern As ExpandCollapsePattern
        If True = elementNode.TryGetCurrentPattern(ExpandCollapsePattern.Pattern, objPattern) Then
            expcolPattern = DirectCast(objPattern, ExpandCollapsePattern)
            If expcolPattern.Current.ExpandCollapseState <> ExpandCollapseState.LeafNode Then
                Dim expcolButton As New Button()
                expcolButton.Margin = New Thickness(0, 0, 0, 5)
                expcolButton.Height = 20
                expcolButton.Width = 100
                expcolButton.Content = "ExpandCollapse"
                expcolButton.Tag = expcolPattern
                AddHandler expcolButton.Click, AddressOf ExpandCollapse_Click
                clientTreeViews(treeviewIndex).Children.Add(expcolButton)
            End If
        End If
        Dim togPattern As TogglePattern
        If True = elementNode.TryGetCurrentPattern(TogglePattern.Pattern, objPattern) Then
            togPattern = DirectCast(objPattern, TogglePattern)
            Dim togButton As New Button()
            togButton.Margin = New Thickness(0, 0, 0, 5)
            togButton.Height = 20
            togButton.Width = 100
            togButton.Content = "Toggle"
            togButton.Tag = togPattern
            AddHandler togButton.Click, AddressOf Toggle_Click
            clientTreeViews(treeviewIndex).Children.Add(togButton)
        End If
        Dim invPattern As InvokePattern
        If True = elementNode.TryGetCurrentPattern(InvokePattern.Pattern, objPattern) Then
            invPattern = DirectCast(objPattern, InvokePattern)
            Dim invButton As New Button()
            invButton.Margin = New Thickness(0)
            invButton.Height = 20
            invButton.Width = 100
            invButton.Content = "Invoke"
            invButton.Tag = invPattern
            AddHandler invButton.Click, AddressOf Invoke_Click
            clientTreeViews(treeviewIndex).Children.Add(invButton)
        End If
        ' Display compiled information about the control.
        elementInfo.Content = elementInfoCompile
        Dim sep As New Separator()
        clientTreeViews(treeviewIndex).Children.Add(sep)

        ' Iterate to next element.
        ' elementNode - Current element.
        ' treeviewIndex - Index of parent TreeView.
        FindTreeViewDescendants(elementNode, treeviewIndex)
        elementNode = TreeWalker.ControlViewWalker.GetNextSibling(elementNode)
    End While

End Sub 'FindTreeViewDescendants

'''--------------------------------------------------------------------
''' <summary>
''' Handles the Invoke click event on the client control. 
''' The client click handler calls Invoke() on the equivalent target control.
''' </summary>
''' <param name="sender">The object that raised the event.</param>
''' <param name="e">Event arguments.</param>
''' <remarks>
''' The Tag property of the FrameworkElement, the client button in this 
''' case, is used to store the InvokePattern object previously obtained 
''' from the associated target control.
''' </remarks>
'''--------------------------------------------------------------------
Private Sub Invoke_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
    Dim clientButton As Button = DirectCast(sender, Button)
    Dim targetInvokePattern As InvokePattern = _
    DirectCast(clientButton.Tag, InvokePattern)
    If (IsNothing(targetInvokePattern)) Then
        Return
    End If
    targetInvokePattern.Invoke()
    statusText.Text = "Button invoked."
End Sub 'Invoke_Click

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