AutomationElement.TryGetCachedPattern(AutomationPattern, Object) Method

Reference

Definition

Namespace:: System.Windows.Automation

Assembly:: UIAutomationClient.dll

Important

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Retrieves a control pattern from the cache.

public:
 bool TryGetCachedPattern(System::Windows::Automation::AutomationPattern ^ pattern, [Runtime::InteropServices::Out] System::Object ^ % patternObject);

public bool TryGetCachedPattern (System.Windows.Automation.AutomationPattern pattern, out object patternObject);

member this.TryGetCachedPattern : System.Windows.Automation.AutomationPattern * obj -> bool

Public Function TryGetCachedPattern (pattern As AutomationPattern, ByRef patternObject As Object) As Boolean

Parameters

pattern: AutomationPattern

The identifier of the control pattern to retrieve.

patternObject: Object

On return, contains the pattern if it is in the cache; otherwise null.

Returns

Boolean

true if the pattern is in the cache; false if it is not in the cache or not supported.

Examples

The following example shows how to cache and retrieve a control pattern.

/// <summary>
/// Caches and retrieves properties for a list item by using CacheRequest.Activate.
/// </summary>
/// <param name="elementList">Element from which to retrieve a child element.</param>
/// <remarks>
/// This code demonstrates various aspects of caching. It is not intended to be 
/// an example of a useful method.
/// </remarks>
private void CachePropertiesByActivate(AutomationElement elementList)
{
    AutomationElement elementListItem;

    // Set up the request.
    CacheRequest cacheRequest = new CacheRequest();
    cacheRequest.Add(AutomationElement.NameProperty);
    cacheRequest.Add(AutomationElement.IsEnabledProperty);
    cacheRequest.Add(SelectionItemPattern.Pattern);
    cacheRequest.Add(SelectionItemPattern.SelectionContainerProperty);

    // Obtain an element and cache the requested items.
    using (cacheRequest.Activate())
    {
        Condition cond = new PropertyCondition(AutomationElement.IsSelectionItemPatternAvailableProperty, true);
        elementListItem = elementList.FindFirst(TreeScope.Children, cond);
    }
    // The CacheRequest is now inactive.

    // Retrieve the cached property and pattern.
    SelectionItemPattern pattern;
    String itemName;
    try
    {
        itemName = elementListItem.Cached.Name;
        pattern = elementListItem.GetCachedPattern(SelectionItemPattern.Pattern) as SelectionItemPattern;
    }
    catch (InvalidOperationException)
    {
        Console.WriteLine("Object was not in cache.");
        return;
    }
    // Alternatively, you can use TryGetCachedPattern to retrieve the cached pattern.
    object cachedPattern;
    if (true == elementListItem.TryGetCachedPattern(SelectionItemPattern.Pattern, out cachedPattern))
    {
        pattern = cachedPattern as SelectionItemPattern;
    }

    // Specified pattern properties are also in the cache.
    AutomationElement parentList = pattern.Cached.SelectionContainer;

    // The following line will raise an exception, because the HelpText property was not cached.
    /*** String itemHelp = elementListItem.Cached.HelpText; ***/

    // Similarly, pattern properties that were not specified in the CacheRequest cannot be 
    // retrieved from the cache. This would raise an exception.
    /*** bool selected = pattern.Cached.IsSelected; ***/

    // This is still a valid call, even though the property is in the cache.
    // Of course, the cached value and the current value are not guaranteed to be the same.
    itemName = elementListItem.Current.Name;
}

''' <summary>
''' Caches and retrieves properties for a list item by using CacheRequest.Activate.
''' </summary>
''' <param name="elementList">Element from which to retrieve a child element.</param>
''' <remarks>
''' This code demonstrates various aspects of caching. It is not intended to be 
''' an example of a useful method.
''' </remarks>
Private Sub CachePropertiesByActivate(ByVal elementList As AutomationElement)

    ' Set up the request.
    Dim myCacheRequest As New CacheRequest()
    myCacheRequest.Add(AutomationElement.NameProperty)
    myCacheRequest.Add(AutomationElement.IsEnabledProperty)
    myCacheRequest.Add(SelectionItemPattern.Pattern)
    myCacheRequest.Add(SelectionItemPattern.SelectionContainerProperty)

    Dim elementListItem As AutomationElement

    ' Obtain an element and cache the requested items.
    Using myCacheRequest.Activate()
        Dim myCondition As New PropertyCondition( _
            AutomationElement.IsSelectionItemPatternAvailableProperty, True)
        elementListItem = elementList.FindFirst(TreeScope.Children, myCondition)
    End Using


    ' The CacheRequest is now inactive.
    ' Retrieve the cached property and pattern.
    Dim pattern As SelectionItemPattern
    Dim itemName As String
    Try
        itemName = elementListItem.Cached.Name
        pattern = DirectCast(elementListItem.GetCachedPattern(SelectionItemPattern.Pattern), _
            SelectionItemPattern)
    Catch ex As InvalidOperationException
        Console.WriteLine("Object was not in cache.")
        Return
    End Try
    ' Alternatively, you can use TryGetCachedPattern to retrieve the cached pattern.
    Dim cachedPattern As Object = Nothing
    If True = elementListItem.TryGetCachedPattern(SelectionItemPattern.Pattern, cachedPattern) Then
        pattern = DirectCast(cachedPattern, SelectionItemPattern)
    End If

    ' Specified pattern properties are also in the cache.
    Dim parentList As AutomationElement = pattern.Cached.SelectionContainer

    ' The following line will raise an exception, because the HelpText property was not cached.
    '** String itemHelp = elementListItem.Cached.HelpText; **

    ' Similarly, pattern properties that were not specified in the CacheRequest cannot be 
    ' retrieved from the cache. This would raise an exception.
    '** bool selected = pattern.Cached.IsSelected; **

    ' This is still a valid call, even though the property is in the cache.
    ' Of course, the cached value and the current value are not guaranteed to be the same.
    itemName = elementListItem.Current.Name
End Sub

Applies to

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