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Friday, December 02, 2005

A resource nightmare on .NET street

Well, I had a fun afternoon. I have a program for the Pocket PC that I just put into alpha. I've written this program using the .NET Compact Framework 1.1. I of course upgraded my development environment to Visual Studio 2005 when it was released about a month ago, however I continued to use version 1.1 of the .NET CF. No problem.

That is, until today when I decided to change one string in my resource file. Once I did that, I kept getting runtime errors when I attempted to read a value from the embedded string resource. First I got an ArgumentError exception, then I got a TypeLoadException. How could that be? My resource code has been working for a long time and I didn't change a single line of code--I just edited the value of a resource string.

After a number of hours trying different things I finally figured it out. I hadn't edited the resource file in quite some time and, as it turned out, I had upgraded the program I was using to edit my resource files, which were in the ".resource" format. I started using a program called Resourcer back when I was using Visual Studio 2002. Recently I decided to get the latest and greatest version, which was labeled ".NET Framework 2.0.50727." What I didn't know, and which now makes sense, is that the author, Lutz Roeder, delivers three different versions of the same program that bind to different versions of the .NET framework. And each of these versions writes a .resource file tied to the same version of the .NET framework.

So when I modified a string and saved the file, Resourcer overwrote the old .NET 1.1 file with a .NET 2.0 file. When I looked more closely at the strings in this file, I noticed that the type for each string is "System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKey Token=b77a5c561934e089." Notice the version number? When I called the resource manager's GetObject method, it attempted to create a 2.0 instance of the type, but this application is running on a device with 1.1 on it, so the create failed.

But the story doesn't end there. I wasn't able to open this file with a "previous" version of Resourcer because the versions for older .NET frameworks weren't able to load the newer types. Fortunately, I was able to use Resourcer to save the file as a .resX file, which I could then include in my project. In the process, I also discovered that Visual Studio 2005 contains a fabulous built-in resource editor that makes Resourcer obsolete.

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