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I have read the page How do I properly clean up Excel interop objects? but I am running into an issue I can't figure out. There is a situation where an Excel instance is embedded and my addin is present causing a hang. I've released all of the COM objects and tried the double GC collection and GC wait lines as suggested for VSTO.

This code below works and doesn't hang.

public static string GetCustomProperty(dynamic document, string propertyName)
{
  string returnVal = string.Empty;
  dynamic customProperties = document.CustomDocumentProperties;

  if (customProperties != null)
  {
    // Nothing
  }

  Marshall.FinalReleaseComObject(customProperties);

  return returnVal;
}

The problem is that once the code changes to this it hangs.

public static string GetCustomProperty(dynamic document, string propertyName)
{
  string returnVal = string.Empty;
  dynamic customProperties = document.CustomDocumentProperties;

  if (customProperties != null)
  {
    foreach (dynamic property in customProperties)
    {
      Marshall.FinalReleaseComObject(property);      
    }
  }

  Marshall.FinalReleaseComObject(customProperties);

  return returnVal;
}

I can't figure out why accessing the objects in customProperties is causing a hang, but commenting out the foreach prevents the hang even when nothing is done inside or FinalReleaseComObject is called. I even tried calling the double GC lines before each marshal of every object and it still hangs. This code is reached from events that handle releasing the workbook the properties come from.

Any ideas as to why the foreach there seems to cause issues?

Community
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user2483770
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1 Answers1

1

I am not sure about your issue, possibly it is related to releasing the COM objects. I don't think the CLR likes you releasing the CustomDocumentProperties, while it is still attached to the WordDocument instance.

This is the code I am using in multiple production environments without any problems. I can remember a lot of issues and errors working with DocumentProperties, but this code seems to be stable.

It gets the DocumentProperty so that is all you have to clean up later.

private object GetDocumentProperty(_Word.Document wordDocument, string name)
{
    try
    {
        return wordDocument.CustomDocumentProperties[name];
    }
    catch (ArgumentException)
    {
        //
        // Key not found.
        //
        return null;
    }
}
Patrick Hofman
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  • I tried your method and it works great. Strangely though, the other way is working now as well. I'm on a different PC now so I will continue testing tomorrow to see if the other PC was just in some kind of weird state that caused the issue. Though I like the idea of passing back the COM object to the caller to handle instead of releasing it in the called function better so that change will probably stay regardless. – user2483770 Dec 04 '14 at 22:07
  • Okay. Good luck and let me hear it if you need help. – Patrick Hofman Dec 04 '14 at 22:08