Updating a DLL in a Production ASP.NET Web Site bin folder

Question

I want to update a class library (a single DLL file) in a production web application. This web app is pre-compiled (published). I read an answer on StackOverflow (sorry, can't seem to find it anymore because the Search function does not work very well), that led me to believe that I could just paste the new DLL in the bin folder and it would be picked up without problems (this would cause the WP to recycle, which is fine with me because we do not use InProc session state).

However, when I tried this, my site blows up and gives a FileLoadException saying that the assembly manifest definition does not match the assembly reference. What in the world is this?! Updating the DLL in Visual Studio and re-deploying the entire site works just fine, but it is a huge pain in the rear. What is the point of having a separate DLL if you have to re-deploy the entire site to implement any changes?

Here's the question: How can I update a DLL on a production web site without breaking the app and without re-deploying all of the files?

Answer 1

The thing to remember is that there are web sites and web applications as far as Visual Studio and ASPNET is considered.

Web Sites typically have all of the aspx and vb files published to the live server and ASPNET Worker Process recompiles the app every time before presentation.

On the other end is the web application, where all of your code behind files get compiled down to a single DLL file and you simply deploy your aspx pages and you bin folder with the DLL file to production.

There is also a "hybrid" known as "Precompiled Web Sites" (see the link for the official MSDN overview) where you don't have the single DLL layout of a web application, but all the compile work of the website is done for you. There are several "modes" to this depending on your needs.

It seems to me that your error is caused because your site is set up as a web site with some kind of precompilation in place. Using the pre-compiled model is a little more "strict" in that is assumes certain files/signatures are in place. Having an updated version of the DLL file causes a break since the precompilation wants a name and a version of the file.

If possible, your best bet would be to convert to a web application, since you can add the additional DLLs into production without a problem. Otherwise, take a look at this matrix to see what form of precompilation you need for your application.

Answer 2

Look at this SO post, might be what you are referring to. The located assembly's manifest definition does not match the assembly reference