TreeWalker Constructor (Condition)


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Initializes a new instance of the TreeWalker class.

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

Public Sub New (
	condition As Condition


Type: System.Windows.Automation.Condition

The view of the UI Automation element tree that TreeWalker will navigate.

UI Automation elements that do not match condition are skipped over when TreeWalker is used to navigate the element tree.

If your client application might try to find elements in its own user interface, you must make all UI Automation calls on a separate thread.

The following example shows how you can construct a TreeWalker that navigates only among enabled elements.

''' <summary>
''' Walks the UI Automation tree and adds the control type of each enabled control 
''' element it finds to a TreeView.
''' </summary>
''' <param name="rootElement">The root of the search on this iteration.</param>
''' <param name="treeNode">The node in the TreeView for this iteration.</param>
''' <remarks>
''' This is a recursive function that maps out the structure of the subtree beginning at the
''' UI Automation element 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 WalkEnabledElements(ByVal rootElement As AutomationElement, ByVal treeNode As TreeNode)
    Dim condition1 As New PropertyCondition(AutomationElement.IsControlElementProperty, True)
    Dim condition2 As New PropertyCondition(AutomationElement.IsEnabledProperty, True)
    Dim walker As New TreeWalker(New AndCondition(condition1, condition2))
    Dim elementNode As AutomationElement = walker.GetFirstChild(rootElement)
    While (elementNode IsNot Nothing)
        Dim childTreeNode As TreeNode = treeNode.Nodes.Add(elementNode.Current.ControlType.LocalizedControlType)
        WalkEnabledElements(elementNode, childTreeNode)
        elementNode = walker.GetNextSibling(elementNode)
    End While

End Sub 'WalkEnabledElements

.NET Framework
Available since 3.0
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