Error: Class Not Registered (0x80040154) when Querying FTP Runtime State

I had a great question from a customer earlier today, and I thought that it was worth blogging about. The problem that he was running into was that he was seeing the following error when he was trying to query the runtime state for the FTP service in an application that he was writing:

Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))

He was using Visual Basic, and his code looked okay to me, so for the moment I was stumped.

I'm more of a C# guy, and I remembered that I had written the following blog many years ago:

Viewing current FTP7 sessions using C#

I copied the code from that blog into a new Visual Studio project, and I got the same error that he was seeing when I ran my code - this had me a little more confused. Have you ever said to yourself, "Darn - I know that worked the other day...?" ;-]

I knew that there is more than one way to access the runtime state, so I rewrote my sample application using two different approaches:

Method #1:

AppHostAdminManager objAdminManager = new AppHostAdminManager();
IAppHostElement objSitesElement =
  objAdminManager.GetAdminSection("system.applicationHost/sites",
  "MACHINE/WEBROOT/APPHOST");
uint intSiteCount = objSitesElement.Collection.Count;
for (int intSite = 0; intSite < intSiteCount; ++intSite)
{
    IAppHostElement objFtpSite = objSitesElement.Collection[intSite];
    Console.WriteLine("Name: " + objFtpSite.Properties["name"].StringValue);
    IAppHostElement objFtpSiteElement = objFtpSite.ChildElements["ftpServer"];
    IAppHostPropertyCollection objProperties = objFtpSiteElement.Properties;
    try
    {
        IAppHostProperty objState = objProperties["state"];
        string ftpState = objState.StringValue;
        Console.WriteLine("State: " + ftpState);
    }
    catch (System.Exception ex)
    {
        Console.WriteLine("\r\nError: {0}", ex.Message);
    }
}

Method #2:

ServerManager manager = new ServerManager();
foreach (Site site in manager.Sites)
{
    Console.WriteLine("Name: " + site.Name);
    ConfigurationElement ftpServer = site.GetChildElement("ftpServer");
    try
    {
        foreach (ConfigurationAttribute attrib in ftpServer.Attributes)
        {
            Console.WriteLine(attrib.Name + ": " + attrib.Value);
        }
    }
    catch (System.Exception ex)
    {
        Console.WriteLine("\r\nError: {0}", ex.Message);
    }
}

Both of these methods returned the same COM error, so this was getting weird for me. Hmm...

The FTP runtime state is exposed through a COM interface, and that is implemented in a DLL that is named "ftpconfigext.dll". That file should be registered when you install IIS, and I re-registered it on my system just for good measure, but that didn't resolve the issue.

I had a brief conversation with one of my coworkers, Eok Kim, about the error that I was seeing. He also suggested re-registering the DLL, but something else that he said about searching the registry for the InprocServer32 entry made me wonder if the whole problem was related to the bitness of my application.

To make a long story short - that was the whole problem.

Both the customer and I were creating 32-bit .NET applications, and the COM interface for the FTP runtime state is implemented in a 64-bit-only DLL. Once we both changed our projects to compile for 64-bit platforms, we were both able to get the code to run. (Coincidentally, all I had was a 32-bit system when I wrote my original blog, so I probably would have run into this sooner if I had owned a 64-bit system way back then. ;-])