You Receive an "Invalid Class" Error Message When You Use a WDM Method (819064)


The information in this article applies to:

  • Microsoft Windows Server 2003, Web Edition
  • Microsoft Windows Server 2003, Standard Edition
  • Microsoft Windows Server 2003, Enterprise Edition
  • Microsoft Windows Server 2003, 64-Bit Enterprise Edition
  • Microsoft Windows Small Business Server 2003, Premium Edition
  • Microsoft Windows Small Business Server 2003, Standard Edition

SYMPTOMS

In Windows Server 2003, when you run a Windows Driver Model (WDM) method, you may receive an "Invalid Class" (WBEM_E_INVALID_CLASS) error message from Windows Management Instrumentation (WMI).

CAUSE

This problem may occur if the method definition in the Managed Object Format (MOF) file contains an OUT parameter first, for example: 
[WmiMethodId(2), Implemented] 
void SampleMethod2([OUT] uint32 Output1,
                   [IN]  uint32 Input1,
                   [IN]  uint32 Input2  );

RESOLUTION

Hotfix Information

A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article. Only apply it to systems that are experiencing this specific problem. This fix may receive additional testing to further ensure product quality. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows Server 2003 service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

File Information

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. 
   Date         Time   Version      Size     File name
   -----------------------------------------------------
   29-May-2003  08:24  5.2.3790.40  137,728  Wmiprov.dll
   29-May-2003  08:24  5.2.3790.40  137,728  Wmisvc.dll

WORKAROUND

To work around this problem, change the order of the [IN] and [OUT] parameters. In the example described in the "Cause" section, change the parameters so that they use the following order:
[WmiMethodId(1), Implemented] 
void SampleMethod1([IN]  uint32 Input1,
                   [IN]  uint32 Input2,
                   [OUT] uint32 Output1);
Note This workaround does not work in Microsoft Windows 2000. In Windows 2000, a problem exists when more than one [IN] parameter is used. If you are using Windows 2000, define the method with the [OUT] parameter first to work around this problem.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

MORE INFORMATION

For more information about WMI, visit the following Microsoft Web site:

http://msdn.microsoft.com/library/en-us/wmisdk/wmi/about_wmi.asp?frame=true

For more information about the MOF language, visit the following Microsoft Web site:

http://msdn.microsoft.com/library/en-us/wmisdk/wmi/managed_object_format.asp?frame=true

For more information about WDM, visit the following Microsoft Web site:

http://www.microsoft.com/whdc/hwdev/driver/wdm/wdm.mspx

Modification Type:MinorLast Reviewed:10/28/2005
Keywords:kbHotfixServer kbQFE kbBug kbfix kbQFE kbWinServ2003preSP1fix KB819064 kbAudITPRO
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