Today while I was working on my usual solution inside Visual Studio I have encountered a serious problem with how Visual Studio, SourceSafe and Web Site projects interact. My solution that I was working with consists of several projects including few Web Sites. My environment is configured to use SourceSafe database as a version control system. Nothing unusual - a 100% Microsoft only environment. I had been working like this without any changes to the configuration for a long time but I noticed that no matter what I do, my solution file (.suo) is growing larger and larger...

Since .suo (solution user options) files only contain information about my options e.g.: opened files, break points etc I thought that it will not hurt much if I just delete this file. I didn't care about opened files nor the location of breakpoints. Besides, sometimes deleting the .suo file is just the only option to restore Visual Studio to a working state after it refuses to open a project file. On top of this, I have deleted the .suo file many times before without any negative effect. So I did again, but this time I was hit right between the eyes and I'm still recovering from the blow.

After deleting the file and starting the solution I got the following message:

"The Open from Source Control operation is still in progress but you can start working now. The rest of the projects will be retrieved asynchronously."

I thought, oh... OK, the message was not a warning and there are a lot of useless messages in Visual Studio so there is no need to worry. I was WRONG, but it came out some time later.

Everything opened correctly and it even seamed to work, but the pages looked different from what I was expecting. They looked exactly the same way as before I made my last changes that I didn't commit before the deletion of .suo file.

After a bit of investigating and testing I have found the problem. And the problem that is! It appears that if you have a file checked out inside of the Web Site project than the fact it is checked out is somehow remembered inside the .suo file. If you delete a .suo file then Visual Studio will try to be "smart" and will get the latest version of that file from the source control - SourceSafe in this case. What this means of course is that any changes in the checked out file will be lost WITHOUT ANY chance to stop and WITHOUT ANY warning message!!!

This issue is only a problem for Web Site projects. Other project types like Class Library are not affected. Now the questions are obvious: why Visual Studio is using .suo files to keep tract of what is checked in and what is checked out inside Web Site projects? Are .scc and .vspscc files not enough? Why would it even try to get the latest version? Is the fact that the file on the disk is not Read Only and is different from the version in the Source Safe not enough to at least issue a warring/question?

In my opinion it is obviously a bug and it has just caused me to lose half a day of work!

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