ExpandCollapsePattern.Collapse Method

public:
 void Collapse();

public void Collapse();

member this.Collapse : unit -> unit

Public Sub Collapse ()

Exceptions

Examples

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 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 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.

See also

• InvokePattern and ExpandCollapsePattern Menu Item Sample