TreeWalker.GetFirstChild Method

public:
 System::Windows::Automation::AutomationElement ^ GetFirstChild(System::Windows::Automation::AutomationElement ^ element);

public System.Windows.Automation.AutomationElement GetFirstChild (System.Windows.Automation.AutomationElement element);

member this.GetFirstChild : System.Windows.Automation.AutomationElement -> System.Windows.Automation.AutomationElement

Public Function GetFirstChild (element As AutomationElement) As AutomationElement

Parameters

Returns

The first child element, or a null reference (Nothing in Visual Basic) if there is no such element.

Examples

The following example shows GetFirstChild being used to construct a tree view of elements in a subtree.

/// <summary>
/// Walks the UI Automation tree and adds the control type of each element it finds 
/// in the control view 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 void WalkControlElements(AutomationElement rootElement, TreeNode treeNode)
{
    // Conditions for the basic views of the subtree (content, control, and raw) 
    // are available as fields of TreeWalker, and one of these is used in the 
    // following code.
    AutomationElement elementNode = TreeWalker.ControlViewWalker.GetFirstChild(rootElement);

    while (elementNode != null)
    {
        TreeNode childTreeNode = treeNode.Nodes.Add(elementNode.Current.ControlType.LocalizedControlType);
        WalkControlElements(elementNode, childTreeNode);
        elementNode = TreeWalker.ControlViewWalker.GetNextSibling(elementNode);
    }
}

''' <summary>
''' Walks the UI Automation tree and adds the control type of each element it finds 
''' in the control view 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 WalkControlElements(ByVal rootElement As AutomationElement, ByVal treeNode As TreeNode)
    ' Conditions for the basic views of the subtree (content, control, and raw) 
    ' are available as fields of TreeWalker, and one of these is used in the 
    ' following code.
    Dim elementNode As AutomationElement = TreeWalker.ControlViewWalker.GetFirstChild(rootElement)

    While (elementNode IsNot Nothing)
        Dim childTreeNode As TreeNode = treeNode.Nodes.Add(elementNode.Current.ControlType.LocalizedControlType)
        WalkControlElements(elementNode, childTreeNode)
        elementNode = TreeWalker.ControlViewWalker.GetNextSibling(elementNode)
    End While

End Sub

Remarks

An AutomationElement can have additional child elements that do not match the current view condition and thus are not returned when navigating the element tree.

The structure of the AutomationElement tree changes as the visible user interface (UI) elements on the desktop change. It is not guaranteed that an element returned as the first child element will be returned as the first child on subsequent passes.

See also

• UI Automation Tree Overview
• Navigate Among UI Automation Elements with TreeWalker
• Obtaining UI Automation Elements

public:
 System::Windows::Automation::AutomationElement ^ GetFirstChild(System::Windows::Automation::AutomationElement ^ element, System::Windows::Automation::CacheRequest ^ request);

public System.Windows.Automation.AutomationElement GetFirstChild (System.Windows.Automation.AutomationElement element, System.Windows.Automation.CacheRequest request);

member this.GetFirstChild : System.Windows.Automation.AutomationElement * System.Windows.Automation.CacheRequest -> System.Windows.Automation.AutomationElement

Public Function GetFirstChild (element As AutomationElement, request As CacheRequest) As AutomationElement

Parameters

Returns

The first child element, or a null reference (Nothing in Visual Basic) if there is no such element.

Remarks

An AutomationElement can have additional child elements that do not match the current view condition and thus are not returned when navigating the element tree.

The structure of the AutomationElement tree changes as the visible user interface (UI) elements on the desktop change. It is not guaranteed that an element returned as the first child element will be returned as the first child on subsequent passes.

See also

• UI Automation Tree Overview
• Navigate Among UI Automation Elements with TreeWalker
• Obtaining UI Automation Elements