Error when instantiating .NET/COM interop class via classic ASP

Question

I am having a problem when trying to instantiate a C# .NET class that's been exposed to COM in a classic ASP application. I've used tlbexp to generate a typelib and registered it in Component Services; now when trying to create the object as such:

Server.CreateObject("The.Class.Name")

I am getting the error:

Server object error 'ASP 0177 : 80131534'

Server.CreateObject Failed

I've searched around online for information on this error, and found numerous discussions but no solution. The error code 0x80131534 apparently means "COR_E_TYPEINITIALIZATION, a type failed to initialize", which would suggest the problem would be in the constructor. The constructor of the class in question sets a private field to an instance of another class from the same assembly, and then reads some configuration settings from an XML file. This behaviour is unit tested and I've checked that the file exists; I can't see anything else that could be breaking in there.

A few other points which may or may not be of use:

• A test .NET project referencing the DLL can instantiate the class just fine; however a test VB6 project referencing the TLB blows up with the same error. Both the DLL and the TLB are in the same location.
• This application is running locally, on Windows XP Professional SP3 and IIS 5.1.
• The .NET assembly is built with .NET Framework 2.0, although 3.5 is installed on the machine.

I know other people who don't get this error on their builds, so I believe it may be something environmental. Any suggestions are welcome as I've been struggling to fix this for some time.

Thanks in advance.

Answer 1

We had exactly the same problem with a class that had a constructor. Funnily enough only on older servers, newer ones would work fine.

We fixed it by adding in a blank public default constructor...

public class MyClass
{
    public string MyGString
    {
        get; set;
    }

    //Com Fix
    public MyClass(){}

    //Normal Class
    public MyClass(string myString)
    {
        HashAlgorithm = hashType;
    }

Someone with the same problem to me...

http://social.msdn.microsoft.com/Forums/vstudio/en-US/4b021da2-3fc7-4f20-b3d0-0f90491a232e/regasm-not-registering-all-classes

Newer servers had this version of RegAsm 2.0.50727.5420 old ones had this version 2.0.50727.3053 This could be something to do with why it worked without a blank public default constructor.

Answer 2

If you can, try using your library from another dynamic, COM enabled language. If you don't know of one, here's a quick snippet that you can use, if you have perl handy. (If you don't, grab ActivePerl to get started really quick)

use strict;
use warnings;
use Win32::OLE;

my $object = Win32::OLE->new('my.object.1')
    or die "Unable to create my.object.1!";
if (my $error = Win32::OLE->LastError()) {
    die "Still got an error starting up: $error\n";
}
print "Good!\n";

Alternatively, if Python is your gig, grab and install PyWin32 and try this:

try:
    import win32com.client as w32c
    from win32com.client import util
except ImportError:
    print "\npywin32 package must be installed.  Available https://sourceforge.net/projects/pywin32/\n"
    sys.exit()
lib = w32c.dynamic.Dispatch("my.object.1")
# error checking and more, yatta

If this works, then it's likely a configuration issue with your ASP app. If this doesn't, then it means the object that you're trying to create either a) isn't registered, or b) has a problem with the library. .NET dll's must be set up properly to export to COM. Was this .NET library one you created yourself?

Answer 3

I'm pretty sure Regasm.exe needs to be used to register a .Net dll to expose it to COM

Interesting post on the subject http://www.simple-talk.com/dotnet/visual-studio/build-and-deploy-a-.net-com-assembly/