ASP.NET publish trying to copy a non-existant file

Update: I went into Project --> Package/Publish Settings, and clicked "Exclude generated debug symbols." The project began publishing with no issue.

Update #2 (this is probably the better answer): I tried to publish as debug instead of release (yes, I wanted to keep the debug features in this particular release), and the error came up again. It turned out that I did not exclude the CKfinder.dll from the project. Once I did so, it ran with no problem.

I also bumped to this problem. I was receiving the following error, when trying to publish MVCForum 1.7:

Copying file App_Data\NuGetBackup\Hello.txt to obj\Release\Package\PackageTmp\App_Data\NuGetBackup\Hello.txt failed. Could not find file 'App_Data\NuGetBackup\Hello.txt'.

François Breton's comment helped me achieve the solution.

It's simple:

Open your .csproj file with a text editor (Notepad, Notepad++) Visual Studio will open it as a project.

Press Ctrl + F and search for the file of the problem. In my case the file was "Hello.txt" without commas.

Under the <ItemGroup> it resided:

<ItemGroup>
<Content Include="App_Data\NuGetBackup\Hello.txt" />
<Content Include="Content\admin\Admin.css">
    <DependentUpon>Admin.scss</DependentUpon>
</Content>
...More code omitted due to brevity.

I deleted the <Content Include="App_Data\NuGetBackup\Hello.txt" /> line, and voila! Visual Studio allowed me to Preview before publishing!

It will end like this:

<ItemGroup>
<Content Include="Content\admin\Admin.css">
    <DependentUpon>Admin.scss</DependentUpon>
</Content>
...More code omitted due to brevity.

Me just removed yellow marked file from my visual studio solution & it worked greatly for me because files were added and removed many times from folders but its not removed from VS solution project.

Delete file showing exclamation mark in the solution explorer. It worked for me