Visual Studio 2010 always thinks project is out of date, but nothing has changed

We also ran into this issue and found out how to resolve it.

The issue was as stated above "The file no longer exists on the disk."

This is not quite correct. The file does exist on the disk, but the .VCPROJ file is referencing the file somewhere else.

You can 'discover' this by going to the "include file view" and clicking on each include file in turn until you find the one that Visual Studio can not find. You then ADD that file (as an existing item) and delete the reference that can not be found and everything is OK.

A valid question is: How can Visual Studio even build if it does not know where the include files are?

We think the .vcproj file has some relative path to the offending file somewhere that it does not show in the Visual Studio GUI, and this accounts for why the project will actually build even though the tree-view of the includes is incorrect.

In Visual Studio 2012 I was able to achieve the same result easier than in the accepted solution.

I changed the option in menu Tools → Options → Projects and Solutions → Build and Run → *MSBuild project build output verbosity" from Minimal to Diagnostic.

Then in the build output I found the same lines by searching for "not up to date":

Project 'blabla' is not up to date. Project item 'c:\foo\bar.xml' has 'Copy to Output Directory' attribute set to 'Copy always'.

This happened to me today. I was able to track down the cause: The project included a header file which no longer existed on disk.

Removing the file from the project solved the problem.

For Visual Studio/Express 2010 only. See other (easier) answers for VS2012, VS2013, etc

To find the missing file(s), use info from the article Enable C++ project system logging to enable debug logging in Visual Studio and let it just tell you what's causing the rebuild:

1. Open the devenv.exe.config file (found in %ProgramFiles%\Microsoft Visual Studio 10.0\Common7\IDE\ or in %ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE\). For Express versions the config file is named V*Express.exe.config.

2. Add the following after the </configSections> line:

   <system.diagnostics>
     <switches>
       <add name="CPS" value="4" />
     </switches>
   </system.diagnostics>
   

3. Restart Visual Studio
4. Open up DbgView and make sure it's capturing debug output
5. Try to debug (hit F5 in Visual Studio)

6. Search the debug log for any lines of the form:

   devenv.exe Information: 0 : Project 'Bla\Bla\Dummy.vcxproj' not up to date because build input 'Bla\Bla\SomeFile.h' is missing.

   (I just hit Ctrl+F and searched for not up to date) These will be the references causing the project to be perpetually "out of date".

To correct this, either remove any references to the missing files from your project, or update the references to indicate their actual locations.

Note: If using 2012 or later then the snippet should be:

<system.diagnostics>
  <switches>
   <add name="CPS" value="Verbose" />
  </switches>
</system.diagnostics>