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Traverse Text Using UI Automation

Note Note

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 shows how to use Microsoft UI Automation to traverse the textual content of a document by TextUnit increments.

The following code example demonstrates how to traverse the content of a UI Automation text provider. The Move method moves the Start and End endpoints of a TextPatternRange. This text range is typically a degenerate range representing the text insertion point.

Note Note

Since only text-based embedded objects are considered part of the text stream, embedded objects such as images do not affect Move or its return value.

///-------------------------------------------------------------------- 
/// <summary> 
/// Starts the target application. 
/// </summary> 
/// <param name="app">
/// The application to start. 
/// </param> 
/// <returns>The automation element for the app main window.</returns> 
/// <remarks> 
/// Three WPF documents, a rich text document, and a plain text document  
/// are provided in the Content folder of the TextProvider project. 
/// </remarks> 
///-------------------------------------------------------------------- 
private AutomationElement StartApp(string app)
{
    // Start application.
    Process p = Process.Start(app);

    // Give the target application some time to start. 
    // For Win32 applications, WaitForInputIdle can be used instead. 
    // Another alternative is to listen for WindowOpened events. 
    // Otherwise, an ArgumentException results when you try to 
    // retrieve an automation element from the window handle.
    Thread.Sleep(2000);

    targetResult.Content =
        WPFTarget +
        " started. \n\nPlease load a document into the target " +
        "application and click the 'Find edit control' button above. " +
        "\n\nNOTE: Documents can be found in the 'Content' folder of the FindText project.";
    targetResult.Background = Brushes.LightGreen;

    // Return the automation element for the app main window. 
    return (AutomationElement.FromHandle(p.MainWindowHandle));
}


...


///-------------------------------------------------------------------- 
/// <summary> 
/// Finds the text control in our target. 
/// </summary> 
/// <param name="src">The object that raised the event.</param>
/// <param name="e">Event arguments.</param>
/// <remarks> 
/// Initializes the TextPattern object and event handlers. 
/// </remarks> 
///-------------------------------------------------------------------- 
private void FindTextProvider_Click(object src, RoutedEventArgs e)
{
    // Set up the conditions for finding the text control.
    PropertyCondition documentControl = new PropertyCondition(
        AutomationElement.ControlTypeProperty,
        ControlType.Document);
    PropertyCondition textPatternAvailable = new PropertyCondition(
        AutomationElement.IsTextPatternAvailableProperty, true);
    AndCondition findControl =
        new AndCondition(documentControl, textPatternAvailable);

    // Get the Automation Element for the first text control found. 
    // For the purposes of this sample it is sufficient to find the  
    // first text control. In other cases there may be multiple text 
    // controls to sort through.
    targetDocument =
        targetWindow.FindFirst(TreeScope.Descendants, findControl);

    // Didn't find a text control. 
    if (targetDocument == null)
    {
        targetResult.Content =
            WPFTarget +
            " does not contain a Document control type.";
        targetResult.Background = Brushes.Salmon;
        startWPFTargetButton.IsEnabled = false;
        return;
    }

    // Get required control patterns 
    targetTextPattern =
        targetDocument.GetCurrentPattern(
        TextPattern.Pattern) as TextPattern;

    // Didn't find a text control that supports TextPattern. 
    if (targetTextPattern == null)
    {
        targetResult.Content =
            WPFTarget +
            " does not contain an element that supports TextPattern.";
        targetResult.Background = Brushes.Salmon;
        startWPFTargetButton.IsEnabled = false;
        return;
    }

    // Text control is available so display the client controls.
    infoGrid.Visibility = Visibility.Visible;

    targetResult.Content =
        "Text provider found.";
    targetResult.Background = Brushes.LightGreen;

    // Initialize the document range for the text of the document.
    documentRange = targetTextPattern.DocumentRange;

    // Initialize the client's search buttons. 
    if (targetTextPattern.DocumentRange.GetText(1).Length > 0)
    {
        searchForwardButton.IsEnabled = true;
    }
    // Initialize the client's search TextBox.
    searchString.IsEnabled = true;

    // Check if the text control supports text selection 
    if (targetTextPattern.SupportedTextSelection ==
        SupportedTextSelection.None)
    {
        targetResult.Content = "Unable to select text.";
        targetResult.Background = Brushes.Salmon;
        return;
    }

    // Edit control found so remove the find button from the client.
    findEditButton.Visibility = Visibility.Collapsed;

    // Initialize the client with the current target selection, if any.
    NotifySelectionChanged();

    // Search starts at beginning of doc and goes forward
    searchBackward = false;

    // Initialize a text changed listener. 
    // An instance of TextPatternRange will become invalid if  
    // one of the following occurs: 
    // 1) The text in the provider changes via some user activity. 
    // 2) ValuePattern.SetValue is used to programatically change  
    // the value of the text in the provider. 
    // The only way the client application can detect if the text  
    // has changed (to ensure that the ranges are still valid),  
    // is by setting a listener for the TextChanged event of  
    // the TextPattern. If this event is raised, the client needs  
    // to update the targetDocumentRange member data to ensure the  
    // user is working with the updated text.  
    // Clients must always anticipate the possibility that the text  
    // can change underneath them.
    Automation.AddAutomationEventHandler(
        TextPattern.TextChangedEvent,
        targetDocument,
        TreeScope.Element,
        TextChanged);

    // Initialize a selection changed listener. 
    // The target selection is reflected in the client.
    Automation.AddAutomationEventHandler(
        TextPattern.TextSelectionChangedEvent,
        targetDocument,
        TreeScope.Element,
        OnTextSelectionChange);
}


...


///-------------------------------------------------------------------- 
/// <summary> 
/// Handles the navigation item selected event. 
/// </summary> 
/// <param name="sender">The object that raised the event.</param>
/// <param name="e">Event arguments.</param>
///-------------------------------------------------------------------- 
private void NavigationUnit_Change(object sender, SelectionChangedEventArgs e)
{
    ComboBox cb = (ComboBox)sender;
    navigationUnit = (TextUnit)cb.SelectedValue;
}

///-------------------------------------------------------------------- 
/// <summary> 
/// Handles the Navigate button click event. 
/// </summary> 
/// <param name="sender">The object that raised the event.</param>
/// <param name="e">Event arguments.</param>
///-------------------------------------------------------------------- 
private void Navigate_Click(object sender, RoutedEventArgs e)
{
    Button moveSelection = (Button)sender;

    // Which direction is the user searching through the text control? 
    int navDirection =
        ((traversalDirection)moveSelection.Tag == traversalDirection.Forward) ? 1 : -1;            

    // Obtain the ranges to move.
    TextPatternRange[] selectionRanges =
                   targetTextPattern.GetSelection();

    // Iterate throught the ranges for a text control that supports 
    // multiple selections and move the selections the specified text 
    // unit and direction. 
    foreach (TextPatternRange textRange in selectionRanges)
    {
        textRange.Move(navigationUnit, navDirection);
        textRange.Select();
   }
   // The WPF target doesn't show selected text as highlighted unless 
   // the window has focus.
   targetDocument.SetFocus();
}

Any method using TextUnit will defer to the next largest TextUnit supported if the given TextUnit is not supported by the control.

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