dotnet/wpf · error · TargetInvocationException

SR.Format(SR.AXNohWnd, GetType().Name)

Error message

SR.Format(SR.AXNohWnd, GetType().Name)

What it means

During ActiveXHost.TransitionFromRunningToInPlaceActive, if the in-place activation of the ActiveX control fails and the control produces no HWND, non-critical failures are rethrown wrapped in a TargetInvocationException with the AXNohWnd message (including the control type name). It signals the control reached a state where WPF cannot host it because no window handle was created.

Solutions

  1. Inspect the InnerException of the TargetInvocationException for the real failure cause from the control.
  2. Re-register the ActiveX control (regsvr32) and verify its COM registration and licensing.
  3. Ensure the control is created on an STA UI thread in an interactive session; avoid hosting in Windows services.
  4. Replace or update the control if it does not support in-place activation with an HWND.

Example fix

// before
try { host.Activate(); }
catch (Exception ex) { Log(ex.Message); }
// after
try { host.Activate(); }
catch (TargetInvocationException tie) {
    Log($"ActiveX failed: {tie.InnerException}"); // real cause
}
Defensive patterns

Strategy: try-catch

Validate before calling

// Verify the control is registered and activatable before hosting:
// Type.GetTypeFromCLSID(clsid) + Activator.CreateInstance smoke test on an STA thread

Try / catch

try
{
    host.TransitionUpTo(ActiveXHelper.ActiveXState.InPlaceActive);
}
catch (TargetInvocationException ex)
{
    var cause = ex.InnerException;
    Log($"ActiveX {host.GetType().Name} failed to activate: {cause}");
}

Prevention

When it happens

Trigger: Calling TransitionUpTo to activate an ActiveX control where the underlying OLE in-place activation fails (returns a failure HRESULT or leaves hWnd zero) with a non-critical exception cause.

Common situations: Broken or unregistered ActiveX controls, controls that refuse in-place activation, missing COM registration, or controls failing under restricted environments (services, non-interactive sessions).

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/b3231e770d55fe6d. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Interop/ActiveXHost.cs:662

        private void TransitionFromRunningToInPlaceActive()
        {
            Debug.Assert(this.ActiveXState == ActiveXHelper.ActiveXState.Running, "Wrong start state to transition from");
            if (this.ActiveXState == ActiveXHelper.ActiveXState.Running)
            {
                try
                {
                    DoVerb(NativeMethods.OLEIVERB_INPLACEACTIVATE);
                }
                catch (Exception e)
                {
                    if(CriticalExceptions.IsCriticalException(e))
                    {
                        throw;
                    }
                    else
                    {
                        throw new TargetInvocationException(SR.Format(SR.AXNohWnd, GetType().Name), e);
                    }
                }

                //
                // We are now InPlaceActive!
                this.ActiveXState = ActiveXHelper.ActiveXState.InPlaceActive;
            }
        }

        private void TransitionFromInPlaceActiveToRunning()
        {
            Debug.Assert(this.ActiveXState == ActiveXHelper.ActiveXState.InPlaceActive, "Wrong start state to transition from");
            if (this.ActiveXState == ActiveXHelper.ActiveXState.InPlaceActive)
            {
                //
                // InPlaceDeactivate.
                _axOleInPlaceObject.InPlaceDeactivate();

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