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ExpandCollapsePattern.Collapse Method

Hides all descendant nodes, controls, or content of the AutomationElement.

Namespace: System.Windows.Automation
Assembly: UIAutomationClient (in uiautomationclient.dll)

'Declaration
Public Sub Collapse
'Usage
Dim instance As ExpandCollapsePattern

instance.Collapse
public void Collapse ()
public function Collapse ()
Not applicable.

Exception typeCondition

InvalidOperationException

Collapse is called when the ExpandCollapseState = LeafNode.

This is a blocking method that returns after the UI Automation element has been collapsed.

There are cases when a UI Automation element 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.

In the following example, a UI Automation element 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 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 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 'ExpandCollapseMenuItem ' TO DO: error handling.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0

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