The original VB.Net source code from Emmet Gray is here:
Visual Studio 2008/2010 Interoperability[
^]
VSProjectConverter is inspired by the original source code provided by Emmet Gray to convert Visual Studio solution and project files from one version to another (both backwards and forwards). The project only supports conversions from Visual Studio 2005 through Visual Studio 2012. This project has been converted to C# and updated to support new features and functionality.
https://github.com/ssvaidya/VSProjectConverter
I just loaded a VS2015 for testing. The program offers it after VS2005, VS2008, VS2010 or VS2013 to convert.
The tool apparently only took care of the solution file and the first line
"Microsoft Visual Studio Solution File, Format Version 12.00"
changed the text to
"Microsoft Visual Studio Solution File, Format Version 8"
You could have done that without a program. Maybe it's because VS2015 is not supported according to the description. But there was also no error message.
For Visual Studio project conversions from earlier versions of Visual Studio (Visual Studio 2002 through
Visual Studio 2008) as well as Visual C++ support, you can check out the Visual Studio Project Converter
project here:
http://sourceforge.net/projects/vspc/
Supported are the following Versions: VS2002, VS2003, VS2005 or VS2008.