WatiN “Unable to cast COM object” exception

问题

from time to time, my monitoring application dies for no obvious reason. It seems like "mshtml.HTMLDocument" resource isn't available. Anyone else experienced something similar? Thanks in advance.

Error message:

14.04.2011 18:26:37 -> Test 1.2 (Subscriber type requests), error: Unable to cast COM object of type 'System.__ComObject' to interface type 'mshtml.HTMLDocument'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{3050F55F-98B5-11CF-BB82-00AA00BDCE0B}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

Error stack trace:

14.04.2011 18:26:37 -> Test 1.2 (Subscriber type requests), trace:    at WatiN.Core.Native.InternetExplorer.IEWaitForComplete.WaitForFramesToComplete(IHTMLDocument2 maindocument)
   at WatiN.Core.Native.InternetExplorer.IEWaitForComplete.WaitForFramesToComplete(IHTMLDocument2 maindocument)
   at WatiN.Core.Native.InternetExplorer.IEWaitForComplete.WaitForCompleteOrTimeout()
   at WatiN.Core.WaitForCompleteBase.DoWait()
   at WatiN.Core.IE.WaitForComplete(Int32 waitForCompleteTimeOut)
   at WatiN.Core.Browser.GoTo(Uri url)
   at WatiN.Core.Browser.GoTo(String url)
   at WebMonitor.Tests.Execute() ...

回答1:

Thanks for reporting. I have put a a re-try around the cast. This exception is probably caused by timing. Hope the re-try will fix it. Will be part of the next release or get the latest code from SourceForge.

来源：https://stackoverflow.com/questions/5664880/watin-unable-to-cast-com-object-exception

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browser

object

com

watin