dotnet/wpf · error · SystemException

SR.Format(SR.OleServicesContext_oleInitializeFailure, hr)

Error message

SR.Format(SR.OleServicesContext_oleInitializeFailure, hr)

What it means

After the STA check, SetDispatcherThread calls the Win32 OleInitialize API to start COM/OLE services on the thread. If OleInitialize returns a failure HRESULT (e.g. RPC_E_CHANGED_MODE or E_OUTOFMEMORY), a SystemException containing the hr is thrown.

Solutions

Ensure the thread is not previously CoInitializeEx'd in MTA mode; keep apartment mode consistent (STA) for the whole thread lifetime.
Inspect the HRESULT in the message (hr) and address the root COM issue (RPC_E_CHANGED_MODE means an apartment-mode conflict).
Move WPF initialization to a fresh, dedicated STA thread that has no prior COM initialization.
If embedding WPF in a native host, initialize COM as STA (CoInitializeEx(NULL, COINIT_APARTMENTTHREADED)) before loading PresentationCore.

Example fix

// before (host code)
CoInitializeEx(NULL, COINIT_MULTITHREADED); // conflicts with WPF OLE init
CreateWpfUi();

// after
CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
CreateWpfUi();

Defensive patterns

Strategy: try-catch

Try / catch

try { InitializeWpfOleServices(); }
catch (SystemException ex) when (ex.Message.Contains("hr"))
{
    // log HRESULT, fall back to non-OLE code path or restart on a clean STA thread
}

Prevention

Initialize COM STA once per thread and never mix COINIT flags.
Create WPF UI on fresh threads without prior CoInitializeEx calls.
Check host application COM initialization when embedding WPF.

When it happens

Trigger: OleInitialize returning S_FALSE-treated-as-failure hr such as RPC_E_CHANGED_MODE when the thread apartment was changed concurrently, or out-of-memory conditions during COM initialization, immediately after the STA check passes.

Common situations: Mixed-mode COM hosting where another component called CoInitializeEx with COINIT_MULTITHREADED on the same thread; COM already initialized differently by a host application (e.g. Office add-ins, COM-shimmed plugins); resource exhaustion on loaded systems.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/762f4bc8637a9c96. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/OleServicesContext.cs:152

    ///  Initialize OleServicesContext that will call Ole initialize for ole services(DragDrop and Clipboard)
    ///  and add the disposed event handler of Dispatcher to clean up resources and uninitalize Ole.
    /// </summary>
    private void SetDispatcherThread()
    {
        int hr;

        if (Thread.CurrentThread.GetApartmentState() != ApartmentState.STA)
        {
            throw new ThreadStateException(SR.OleServicesContext_ThreadMustBeSTA);
        }

        // Initialize Ole services.
        // Balanced with OleUninitialize call in OnDispatcherShutdown.
        hr = OleInitialize();

        if (!NativeMethods.Succeeded(hr))
        {
            throw new SystemException(SR.Format(SR.OleServicesContext_oleInitializeFailure, hr));
        }

        // Add Dispatcher.Shutdown event handler. 
        // We will call ole Uninitialize and clean up the resource when UIContext is terminated.
        Dispatcher.CurrentDispatcher.ShutdownFinished += new EventHandler(OnDispatcherShutdown);
    }

    /// <summary>
    ///  This is a callback when the <see cref="Dispatcher"/> is shut down.
    /// </summary>
    /// <remarks>
    ///  <para>
    ///   This method must be called before shutting down the application on the dispatcher thread. It must be called
    ///   by the same thread running the dispatcher and the thread must have its ApartmentState property set to
    ///   <see cref="ApartmentState.STA"/>.
    ///  </para>
    /// </remarks>
    private void OnDispatcherShutdown(object sender, EventArgs args)

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