dotnet/wpf · error · InvalidOperationException

SR.CantPrefetchTextPattern

Error message

SR.CantPrefetchTextPattern

What it means

TextPattern.Wrap (internal factory) throws InvalidOperationException when the SafePatternHandle handed to it is invalid — i.e. the text pattern handle could not be prefetched/resolved from the UIA core for the element. This indicates the element no longer exposes the Text pattern or the underlying handle acquisition failed.

Solutions

1. Check TextPattern.IsAvailable / GetSupportedPatterns immediately before requesting the pattern and again after failures.
2. Catch InvalidOperationException and ElementNotAvailableException around pattern retrieval and re-find the element via a fresh AutomationElement.
3. Use AutomationEventHandler for structure changes to stop operating on dead elements.

Example fix

// before
var tp = (TextPattern)element.GetCurrentPattern(TextPattern.Pattern); // may throw
// after
if (!element.TryGetCurrentPattern(TextPattern.Pattern, out var obj)) return null;
var tp = (TextPattern)obj;

if (!element.GetSupportedPatterns().Any(p => p.ProgrammaticName == TextPattern.Pattern.ProgrammaticName)) return null;

try
{
    element.GetCurrentPattern(TextPattern.Pattern);
}
catch (InvalidOperationException)
{
    element = ReFindElement(searchCriteria); // pattern handle invalid; re-acquire
}
catch (ElementNotAvailableException) { /* element gone */ }

When it happens

Trigger: Retrieving TextPattern via AutomationElement.GetCurrentPattern(TextPattern.Pattern) (or GetSupportedPattern) from an element whose provider no longer supports Text, or after the element was removed/disconnected so the native pattern handle is invalid.

Common situations: Target UI vanished (document closed, window destroyed) between finding the element and fetching the pattern; provider regression where TextPattern.IsAvailable was true but the handle could not be created; race conditions in automation scripts.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• Character offset not valid in TextRange.
• E_OUTOFMEMORY
• Element no longer available.
• Element no longer available.
• ElementNotAvailableException

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/b821925f0d2ecb71. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClient/System/Windows/Automation/TextPattern.cs:275

            {
                return UiaCoreApi.TextPattern_get_SupportedTextSelection(_hPattern);
            }
        }

        #endregion Public Properties

        //------------------------------------------------------
        //
        //  Internal Methods
        //
        //------------------------------------------------------
 
        #region Internal Methods
        internal static object Wrap(AutomationElement el, SafePatternHandle hPattern, bool cached)
        {
            if (hPattern.IsInvalid)
            {
                throw new InvalidOperationException(SR.CantPrefetchTextPattern);
            }

            return new TextPattern(el, hPattern);
        }

        // compare two text patterns and return true if they are from the same logical element.
        internal static bool Compare(TextPattern t1, TextPattern t2)
        {
            return Misc.Compare(t1._element, t2._element);
        }

        #endregion Internal Methods
        
        //------------------------------------------------------
        //
        //  Private Fields
        //
        //------------------------------------------------------

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