Strange error packaging app with Visual Studio

I'm using VS2017 to convert and package a desktop application to upload to Microsoft App Store. I did as this instruction:

https://docs.microsoft.com/en-us/windows/uwp/porting/desktop-to-uwp-packaging-dot-net

Everything went smooth and I can compile the package project. However when creating the .appxupload an error occurs

In the figure WindowsFormsTrussApp is the desktop application and WindowsFormsTrussAppPackage is the packaging project. It is linked with the desktop application.

The error message is:

7>Build FAILED. 7> 7>MakeAppx : error : Manifest validation error: Line 20, Column 27, Reason: The file name "WindowsFormsTrussAppPackage.exe" declared for element "[local-name()='Applications']/[local-name()='Application']" doesn't exist in the package. 7>MakeAppx : error : Package creation failed. 7>MakeAppx : error : 0x80080204 - The specified package format is not valid: The package manifest is not valid. 7> 0 Warning(s) 7> 3 Error(s)

The WindowsFormsTrussAppPackage.exe is not supposed to be created, since it is not produced during compilation. I have no idea how this error happens.