FIX: You receive a "NullReferenceException" error message when you try to pass a .NET Framework class to a COM wrapper class (328557)

SYMPTOMS

In an application that is built on the Microsoft .NET Framework, you call a COM function that accepts a pointer to a COM interface as its parameter. If you then pass to the function a .NET Framework class that implements a wrapper interface that is created around the COM interface, the function call does not succeed and you receive the following error message:

An unhandled exception of type 'System.NullReferenceException' occurred in YourApp.exe Additional information:
Object reference not set to an instance of an object.

CAUSE

This problem occurs because the wrapper class that the Type Library Importer utility (Tlbimp.exe) generates for the COM interface changes the COM function definition so that the function accepts a .NET Framework wrapper interface instead of the actual COM interface pointer.

Note The Type Library Importer utility only does this for the default interface for coclasses. If you use an interface that is not the default interface for a coclass, the application works as expected.

RESOLUTION

How to obtain the hotfix

This issue is fixed in the Post-Service Pack 2 .NET Framework Core CLR Hotfix Package. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

328544 INFO: Post-Service Pack 2 .NET Framework Core CLR Hotfix Package

Hotfix information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft .NET Framework 1.0 service pack that contains this hotfix.

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

http://support.microsoft.com/contactus/?ws=support

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.

The English version of this hotfix 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
   ---------------------------------------------------------
   06-Aug-2002  20:00  1.0.3705.292  1,953,792  Mscorlib.dll
   14-Aug-2002  18:23  1.0.3705.292  3,039,232  Mscorsvr.dll
   14-Aug-2002  18:23  1.0.3705.292  3,035,136  Mscorwks.dll

MORE INFORMATION

For additional information about this problem, including a workaround and the steps to reproduce this problem, click the following article number to view the article in the Microsoft Knowledge Base:

318608 FIX: Tlbimp.exe generates interface wrappers that cannot be used

For additional information about the terminology that is used to describe Microsoft product updates, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates