ExpandCollapsePattern.Expand Method

Reference

Definition

Namespace:: System.Windows.Automation

Assembly:: UIAutomationClient.dll

Important

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Displays all child nodes, controls, or content of the AutomationElement.

public:
 void Expand();

public void Expand ();

member this.Expand : unit -> unit

Public Sub Expand ()

Exceptions

InvalidOperationException

Expand() is called when the ExpandCollapseState = LeafNode.

Examples

In the following example, an AutomationElement representing a menu item is passed to a function that attempts to expand or collapse the menu item based on its current ExpandCollapseState.

///--------------------------------------------------------------------
/// <summary>
/// Obtains an ExpandCollapsePattern control pattern from an 
/// automation element.
/// </summary>
/// <param name="targetControl">
/// The automation element of interest.
/// </param>
/// <returns>
/// A ExpandCollapsePattern object.
/// </returns>
///--------------------------------------------------------------------
private ExpandCollapsePattern GetExpandCollapsePattern(
    AutomationElement targetControl)
{
    ExpandCollapsePattern expandCollapsePattern = null;

    try
    {
        expandCollapsePattern =
            targetControl.GetCurrentPattern(
            ExpandCollapsePattern.Pattern)
            as ExpandCollapsePattern;
    }
    // Object doesn't support the ExpandCollapsePattern control pattern.
    catch (InvalidOperationException)
    {
        return null;
    }

    return expandCollapsePattern;
}

'''--------------------------------------------------------------------
''' <summary>
''' Obtains an ExpandCollapsePattern control pattern from an 
''' automation element.
''' </summary>
''' <param name="targetControl">
''' The automation element of interest.
''' </param>
''' <returns>
''' A ExpandCollapsePattern object.
''' </returns>
'''--------------------------------------------------------------------
Private Function GetExpandCollapsePattern( _
ByVal targetControl As AutomationElement) As ExpandCollapsePattern
    Dim expandCollapsePattern As ExpandCollapsePattern = Nothing

    Try
        expandCollapsePattern = DirectCast( _
        targetControl.GetCurrentPattern(expandCollapsePattern.Pattern), _
        ExpandCollapsePattern)
    Catch exc As InvalidOperationException
        ' Object doesn't support the ExpandCollapsePattern control pattern.
        Return Nothing
    End Try

    Return expandCollapsePattern

End Function 'GetExpandCollapsePattern

///--------------------------------------------------------------------
/// <summary>
/// Programmatically expand or collapse a menu item.
/// </summary>
/// <param name="menuItem">
/// The target menu item.
/// </param>
///--------------------------------------------------------------------
private void ExpandCollapseMenuItem(
    AutomationElement menuItem)
{
    if (menuItem == null)
    {
        throw new ArgumentNullException(
            "AutomationElement argument cannot be null.");
    }

    ExpandCollapsePattern expandCollapsePattern =
        GetExpandCollapsePattern(menuItem);

    if (expandCollapsePattern == null)
    {
        return;
    }

    if (expandCollapsePattern.Current.ExpandCollapseState ==
        ExpandCollapseState.LeafNode)
    {
        return;
    }

    try
    {
        if (expandCollapsePattern.Current.ExpandCollapseState == ExpandCollapseState.Expanded)
        {
            // Collapse the menu item.
            expandCollapsePattern.Collapse();
        }
        else if (expandCollapsePattern.Current.ExpandCollapseState == ExpandCollapseState.Collapsed ||
            expandCollapsePattern.Current.ExpandCollapseState == ExpandCollapseState.PartiallyExpanded)
        {
            // Expand the menu item.
            expandCollapsePattern.Expand();
        }
    }
    // Control is not enabled
    catch (ElementNotEnabledException)
    {
        // TO DO: error handling.
    }
    // Control is unable to perform operation.
    catch (InvalidOperationException)
    {
        // TO DO: error handling.
    }
}

'''--------------------------------------------------------------------
''' <summary>
''' Programmatically expand or collapse a menu item.
''' </summary>
''' <param name="menuItem">
''' The target menu item.
''' </param>
'''--------------------------------------------------------------------
Private Sub ExpandCollapseMenuItem(ByVal menuItem As AutomationElement)
    If menuItem Is Nothing Then
        Throw New ArgumentNullException( _
        "AutomationElement argument cannot be null.")
    End If

    Dim expandCollapsePattern As ExpandCollapsePattern = _
    GetExpandCollapsePattern(menuItem)

    If expandCollapsePattern Is Nothing Then
        Return
    End If

    If expandCollapsePattern.Current.ExpandCollapseState = _
    ExpandCollapseState.LeafNode Then
        Return
    End If

    Try
        If expandCollapsePattern.Current.ExpandCollapseState = _
        ExpandCollapseState.Expanded Then
            ' Collapse the menu item.
            expandCollapsePattern.Collapse()

        ElseIf expandCollapsePattern.Current.ExpandCollapseState = _
        ExpandCollapseState.Collapsed OrElse _
        expandCollapsePattern.Current.ExpandCollapseState = _
        ExpandCollapseState.PartiallyExpanded Then
            ' Expand the menu item.
            expandCollapsePattern.Expand()
        End If
    Catch exc As ElementNotEnabledException
        ' Control is not enabled
        ' TO DO: error handling.
    Catch exc As InvalidOperationException
        ' Control is unable to perform operation 
        ' TO DO: error handling.
    End Try

End Sub

Remarks

This is a blocking method that returns after the AutomationElement has been expanded.

There are cases when a AutomationElement that is marked as a leaf node might not know whether it has children until either the Collapse or the Expand method is called. This behavior is possible with a tree view control that does delayed loading of its child items. For example, Microsoft Windows Explorer might display the expand icon for a node even though there are currently no child items; when the icon is clicked, the control polls for child items, finds none, and removes the expand icon. In these cases clients should listen for a property-changed event on the ExpandCollapseState property by registering an event handler with the AddAutomationPropertyChangedEventHandler method.

Applies to

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