I was working on a feature last week that would add some event receivers to a specific list instance.  (I blogged a bit about that list receiver here).

Using the command line, I could install the feature with no error (but see below for the hidden error).  When I tried to deploy the feature on the site, MOSS complained of a "FileNotFoundException" error.  This blog entry describes how I solved it. 

This is the error that MOSS showed me in the web browser:

Feature ‘b2cb42e3-4f0a-4380-aaba-1ef9cd526f20’ could not be installed because the loading of event receiver assembly "xyzzyFeatureReceiver_0" failed: System.IO.FileNotFoundException: Could not load file or assembly ‘xyzzyFeatureReceiver_0’ or one of its dependencies. The system cannot find the file specified. File name: ‘xyzzyFeatureReceiver_0’    at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)    at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)    at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)    at System.Reflection.Assembly.Load(String assemblyString)    at Microsoft.SharePoint.Administration.SPFeatureDefinition.get_ReceiverObject() WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. Troubleshoot issues with Windows SharePoint Services.

I know how to deliberately cause that error: don’t install the assembly in the GAC.  But, it was in the GAC.  I normally install assemblies into the GAC by dragging them into the c:\windows\assembly folder using windows explorer.  I’ve never felt 100% comfortable doing that because I always thought that gacutil existed for a reason … so I tried that.  It made no difference.

I searched the Internets and found this post: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=2243677&SiteID=1

The poster happened to be using the same root bit of code (from the Inside WSS book from this list) so that was a hopeful sign.  However, the suggestion of decorating the assembly with an [assembly: ] directive didn’t make sense to me.  I tried it anyway and I was right.  It made no difference.

Then I noticed that my class definition was not public.  I made it public and that made no difference.

Next, I went to the trouble of enabling the "assembly bind failure log" (following the helpful and accurate instructions provided) and this is where things started to get interesting.  That log shows me that the runtime is searching everywhere on that server for my assembly.  It even appears to be searching for it in my medicine cabinet.  But … it won’t search for it in the GAC.

I put on my winter jacket and go searching the Internets again and find that someone has had this problem too.  The lengthy discussion in that posting peters off into nothing and I can’t find a solution.

I move my assembly into one of the places the log claims it’s searching and I make a little more progress.  I’m rewarded with a new error in the browser when I try to activate the feature:

Failed to create feature receiver object from assembly "xyzzyFeatureReceiver_0", type "Conchango.xyzzyFeatureReceiver" for feature b2cb42e3-4f0a-4380-aaba-1ef9cd526f20: System.ArgumentNullException: Value cannot be null. Parameter name: type    at System.Activator.CreateInstance(Type type, Boolean nonPublic)    at System.Activator.CreateInstance(Type type)    at Microsoft.SharePoint.Administration.SPFeatureDefinition.get_ReceiverObject() Troubleshoot issues with Windows SharePoint Services.

Time for one last trip to the Internets!

This time I find out, predictably enough, that MOSS issues this error because the assembly is not in GAC. 

I want to get something positive out of this and try to feel a little proud that I’ve created the Fugitive of MSIL assemblies, but it’s not working.  I’m just plain annoyed.  I find myself muttering "chicken or the egg" under my breath.

I finally decide to punt.  I create an entirely new project and copy/paste the code from the incredible-cloaked-from-the-GAC-assembly non-working project over to this new project.  (I look for a build flag called something like "hide from assembly binding if installed in the GAC" but can’t find one).

I install the feature and activate it and … it works!  So, after all that, I had to basically ‘reboot’ my project.  This is another reason why I hate computers.

I did learn something useful  from this.  I had been installing features using the stsadm command line all day long and been using the "-force" option out of habit.  For some reason, I did not use the -force option when I installed the new project.  This time, I did actually, truly forget to copy this new project’s assembly into the GAC.  As a result, I received that "FielNotFoundException" error.  This time, I got it from stsadm, not when I tried to activate the feature via the web browser.  So, -force actually plays two roles.  It allows you to re-install an existing feature.  It also allows you to install a buggy feature that cannot work at runtime by suppressing the error.  It probably says as much in the help somewhere but I never noticed it.

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UPDATE: This works but there are significant limitations which are described in the comments.  This may still be useful in some cirumstances.

UPDATE 2: In my current project, users always upload documents.  As a result, I don’t run into a problem where MS Word is running and thinks that the file was renamed on it.  I did run into a problem, "the file was modified by someone else" and solved this via a simple semaphore type flag.  Users need to change a meta data field from its default value to something else.  The itemupdated() receiver looks for a valid value there before actually performing the rename and since then, I have not had any problems.  Your mileage may vary.

I have a client requirement to change the name of files uploaded to a specific document library to conform with a particular naming convention.  The API does not provide a "rename()" method.  Instead, we use "MoveTo(…)".  Here is a minimal bit of code to accomplish this:

 public override void ItemAdded(SPItemEventProperties properties)
        {
            SPFile f = properties.ListItem.File;

            f.MoveTo(properties.ListItem.ParentList.RootFolder.Url + "/xyzzy.doc");
            f.Update();

        }

The only tricky bit is the "properties.ListItem.ParentList.RootFolder.Url".  The MoveTo() method requires a URL.  That mashed up string points me to the root folder of my current document library.  This allows me to avoid any hard coding in my event receiver.

This is a more useful version that does the same thing, but assigns the name of the file to "Title":

 public override void ItemAdded(SPItemEventProperties properties)
        {
            DisableEventFiring();

            // Assign the title of this item to the name of file itself.
 // NOTE: This assignment must take place before we modify the file itself.
 // Calling update() on the SPFile seems to invalidate the properties in
 // some sense.  Updates to "Title" failed until that change (and update() call)
 // were moved in front of the change to the file name.
            properties.ListItem["Title"] = properties.ListItem.File.Name;

            properties.ListItem.Update();

            SPFile f = properties.ListItem.File;

            // Get the extension of the file.  We need that later.
 string spfileExt = new FileInfo(f.Name).Extension;

            // Rename the file to the list item's ID and use the file extension to keep
 // that part of it intact.
            f.MoveTo(properties.ListItem.ParentList.RootFolder.Url +
                "/" + properties.ListItem["ID"] + spfileExt);

            // Commit the move.
            f.Update();

            EnableEventFiring();
        }