I was misled by the C++ “Empty Project” or “Makefile Project”. I cant create new folder there.
Here are three steps to add an empty C# project:
1) Create the project. (Add > New Project > Visual C# > Windows > Empty Project)
2) Exclude it from build. (Build > Configuration Manager, uncheck Build on both Debug and Release configuration)
3) Replace its csproj content with the following 3 liners:
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
</Project>
There you go. You can create a folder in this project, yet it does not build.