How To Get the HRESULT From a COM Object (186298)


The information in this article applies to:

  • Microsoft Visual FoxPro for Windows 3.0
  • Microsoft Visual FoxPro for Windows 3.0b
  • Microsoft Visual FoxPro for Windows 5.0
  • Microsoft Visual FoxPro for Windows 5.0a
This article was previously published under Q186298

SUMMARY

When you make calls to a function of a COM interface, the function returns an integer return code, or HRESULT. This value consists of a severity code, context information, a facility code, and a status code that describes the result. In Visual FoxPro, it may be useful to obtain the HRESULT for debugging purposes or error handling.

MORE INFORMATION

In Visual FoxPro, it is not possible to obtain the HRESULT directly. However, when an OLE error occurs (error number 1426), the HRESULT is in the text of the error message in the form 0x800nnnnn. The sample code below demonstrates how to extract the HRESULT from the error message text and display it in both base 10 and hexadecimal format.

Sample Code

Create a program file named Hresult.prg, with the following code: 
   *-- Code begins here.
   ON ERROR DO getresult IN hresult WITH ;
      ERROR(), MESSAGE()

   *-- Create an instance of Microsoft Word.
   oWord = CREATEOBJECT("Word.Application")

   *-- Call an invalid function to test our error handling.
   oWord.RaiseError

   PROCEDURE getresult
      PARAMETER liError, lsMessage

   IF liError <> 1426  && Not an OLE error code

      *-- Since this error handler now handles all errors, it
      *-- would be best to include some more robust error
      *-- handling here to handle errors other than #1426.
      RETURN
   ENDIF

   *-- Take the message string and parse the hexadecimal HRESULT.
   *-- The VAL() function will do the conversion to a base 10 integer.
   liHresult = VAL(SUBSTR(lsMessage, AT("0x", lsMessage), 10))

   *-- Display the result in decimal and hexadecimal format.
   *-- This section would be used to process the HRESULT as needed,
   *-- either by parsing the returned code or otherwise overriding the
   *-- default Visual FoxPro behavior.
   MESSAGEBOX("OLE function returned HRESULT: " +;
     CHR(10) + CHR(13) + ;
     STR(liHresult) + " (decimal) " +;
     CHR(10) + CHR(13) + ;
     TRANSFORM(liHresult, "@0") + " (hexadecimal)", 0, "OLE Error")
   RETURN
   *-- Code ends here.

REFERENCES

MSDN Library

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Mike Stewart, Microsoft Corporation
Modification Type:MinorLast Reviewed:7/1/2004
Keywords:kbhowto KB186298
©2004 Microsoft Corporation. All rights reserved.