Web Application Project Issues 101: "Could Not Load Type..."

By
One *Extremely* common newsgroup and forum post I've seen recently revolves around "double compilation" of stuff that was left in the APP_CODE folder when a project is migrated from WebSite mode to Web Application Project. For starters, I'll quote directly from "Mr. ASP.NET" Scott Guthrie's blog tutorial:

"VERY, VERY IMPORTANT: Because ASP.NET 2.0 tries to dynamically compile any classes it finds under the /App_Code directory of an application at runtime, you explictly *DO NOT* want to store classes that you compile as part of your VS 2005 Web Application Project under an "app_code" folder. If you do this, then the class will get compiled twice -- once as part of the VS 2005 Web Application Project assembly, and then again at runtime by ASP.NET. The result will most likely be a "could not load type" runtime exception -- caused because you have duplicate type names in your application. Instead, you should store your class files in any other directory of your project other than one named "app_code". This will be handled automatically by the "Convert to Web Application" command. This command will rename the folder Old_App_Code."

This should be very clear, but apparently (as one would expect) a lot of developers don't take the time to read the tutorials that kind Mr. Guthrie has literally toiled over for your benefit! I should mention as a footnote that you need to choose the context menu item "Convert to Web Application Project" at the PROJECT level in your Solution Explorer node in order for this to occur.

There's another little "gotcha" that I bet you have run into, and there's a fix for that too, if you just take the time to "RTFM":

VS 2005 Web Application Projects don't automatically support generating a strongly-typed Profile class proxy. However, you can use this free download to automatically keep your own proxy class in sync with the profile configuration. Now, I'll be the first to admit that this little guy can be very tricky in getting "Profile.Common" to come alive, but once you understand what it is doing, you'll have taken the first step to "Conversion"!

Moral of the story: Not to sound like a broken MP3, but "Read the Manual" (in this case, the nice tutorials!). Or, phrased another way: There are two kinds of professional developers in the world: Those that take the time to read the manual, -- and those that take the time to read the manual.


There is no other way. More later.
Peter has been active on the C# and other MS newsgroups, has had samples at gotdotnet.com (now codegallery.com) that have been downloaded over 56,000 times, and has written numerous articles for eggheadcafe.com, for which he is a co-founder, and MSDNAA sites. He has also been a technical reviewer on books from Prentice Hall, Manning and other publishers. Peter was a Microsoft MVP for 10 years. Peter was born and raised in New York City, and after a stint as a jazz musician playing contrabass with the Robert Hunt Trio, migrated to sunny Florida, where he was hired as a rookie Financial Consultant at Merrill Lynch in Orlando, specializing in Corporate Services. It was at Merrill that Peter realized computers and technology were his forte. He spent his last few years at Merrill developing real – time computerized trading and and stock charting program using advanced technical analysis indicators, some of which are his own inventions. In 1997, he moved on to architect and serve as lead developer on a number of innovative web-based and middleware solutions for the healthcare and financial services industry.

Comments

Post a Comment

Popular posts from this blog

Some observations on Script Callbacks, "AJAX", "ATLAS" "AHAB" and where it's all going.

By
I've taken a more than cursory interest in the whole Remote Scripting (.NET species) vs. AJAX and now ATLAS discussion, mostly because I started using Remote Scripting since Microsoft first released it, and because I continued to refine it after seeing Brent Ashley's excellent work with JSRS, which was one of the first "real" cross-browser solutions back in 2000 (that's the turn of the Century for you history buffs). Now Bertrand Leroy, a Microsoft guy whose work I like , has authored some very interesting ASP.NET 2.0 script callback stuff that he points to on his blog, and he is obviously (at least, to me he is) involved quite heavily in the development of this new ATLAS infrastructure that they'll preview at PDC. Leroy's most recent post brings to the surface what I agree are the major differences between the "AJAX a - la .NET" approach as popularized by Michael Swartz with his AJAX.NET library, and Leroy's RefreshPanel, the ASP.NET 2.0 b...
Read more

IE7 - Vista: "Internet Explorer has stopped Working"

By
Image
This one was a bitch. All of a sudden for no reason at all, out of the blue, I get this dialog "internet Explorer has stopped working". I didn't install any new software, crap- I didn't do anything! So here I am using FIREFART to go on the internet and find out what to do! Damn! Good thing I've got the sucker on the same machine (I'm not "anti-Firefox", i just don't use it that much except to check my page renderings). The Fix The fix (at least for me): 1) Go into Control Panel, and choose "Internet Options". 2) Under the "Advanced" tab, press the "RESET" button at the lower right: Don't ask me why this happens, or why the fix works. That's a BUG, D00D - I don't care how you slice it!
Read more

FIREFOX / IE Word-Wrap, Word-Break, TABLES FIX

By
One of the most annoying things a developer (who would normally delight in writing code, not futzing with markup) can have is getting rendering issues between different browsers. The two biggest players are of course Internet Exploder and Firefart (as I lovingly like to refer to each). In most cases that's going to take care of 98 percent of your total site traffic. IE has had a proprietary "word-break" style attribute for a long time, and this made it into the CSS 3.0 spec. But that doesn't necessarily help you with Firefox right now. Firefox literally - (and I consider this completely idiotic, since it's been in their bug database for FIVE YEARS) does not have a reliable CSS style element to force table cell content to break in the middle of a word in order to stop the content from expanding your table / div off the page or over other content on the page. Here's a partial fix, which will work for most tables and browsers. The style declaration (I call it m...
Read more

System.Web.Caching.Cache, HttpRuntime.Cache, and IIS Recycles

By
Recently I chimed in on a newsgroup thread to an OP (Original Poster) who was questioning why he was losing Cache items. This individual would load a dataset from the Cache object into a local object to use to perform processing. He had been using httpcontext.current.cache and noticed that sometimes he was not able to get the dataset out of the cache. He tried switching to HttpRuntime.Cache and it seemed to help. The OP claimed that the application is under heavy hits, and once or twice every month he would see this error. He wanted to know why does the HttpContext.Current.Cache call work sometimes, while some other times does not. A couple of posters replied, one of whom is a respected MVP who usually makes very astute, high-quality posts. He posted," The cache is only valid during the life of the request. how is you[sic] code using the cache?" Somebody else (also pretty astute, usually) responded, "Cache is valid during lifetime of application not request.....". W...
Read more

FIX: Requested Registry Access is not allowed (Visual Studio 2008)

By
Symptom: in Visual Studio 2008, you attempt to add a new WebContentForm and associate it with a MasterPage. You receive an error dialog "Requested Reqistry Access is not allowed". Don't ask me what caused this; I'm guessing that the registry keys involved had their access denied due to removal of a previous version of Visual Studio, leaving the new guy (Visual Studio 2008) in the lurch. Here's the fix: Download "subinacl" here . This is a command-line tool that enables administrators to obtain security information about files, registry keys, and services, and transfer this information from user to user, from local or global group to group, and from domain to domain. After installing subinacl.exe (it will be in the C:\Program Files\Windows Resource Kits\Tools folder.), drop to a command prompt and run the following batch file, which you have saved in the same folder with the filename "FIX.bat": subinacl /subkeyreg HKEY_CLASSES_ROOT\VisualStudi...
Read more