invalidIUnknown MDA

  • Article

Note

This article is specific to .NET Framework. It doesn't apply to newer implementations of .NET, including .NET 6 and later versions.

The invalidIUnknown managed debugging assistant (MDA) is activated when an invalid IUnknown pointer is passed to managed code from native code. The IUnknown fails to return success when queried for the IUnknown interface.

Symptoms

An unexpected error occurs when marshalling a COM interface pointer during argument marshalling.

Cause

An incorrect QueryInterface implementation on the COM interface passed to the CLR.

Resolution

Correct the QueryInterface implementation.

Effect on the Runtime

This MDA has no effect on the CLR.

Output

The description of the error.

Configuration

<mdaConfig>
  <assistants>
    <invalidIUnknown />
  </assistants>
</mdaConfig>

See also