Projected File System (ProjFS)

The ProjectedFileSystem class is still provided with ShellBoost for compatibility reasons but will not evolve, since Microsoft now provides a Managed API over the native Windows one: https://github.com/microsoft/ProjFS-Managed-API.

Windows 10 version 1809 has introduced the “Projected File System” feature, only for NTFS physical drives and only for 64-bit applications.

Although this technology is not strictly related to Shell Namespace Extension development (in fact, it’s not even related to the Shell, it operates at the lower File System level), ShellBoost provides some exclusive support for it, in combination with Shell Namespace Extension development, through the ProjectedFileSystem and ProjectedFileSystemProvider classes.

The Windows Projected File System (ProjFS) allows a user-mode application called a "provider" to project hierarchical data into the file system, making it appear as files and directories in the file system. For example, a simple provider could project the Windows registry into the file system, making registry keys and values appear as files and directories, respectively. An example of a more complex provider is VFS for Git, used to virtualize very large git repos.