File.Move of HttpPostedFileBase file

I have a web page that takes an uploaded file, processes it then I am attempting to move it to another file folder.  This all happens on a single server.

The import UI looks like this:

 

This is the .cshtml for the UI

 

 

This is the controller method attempting to move the file

I am getting the error: 

 

However, I know the file is not being used by anyone else during this process.  I have tested the process on several files.

 

In the controller, I am both closing and disposing of the file input stream.   

Please help me resolve this matter.

 

Thank you, 

 

Update: I am using ASP Net MVC 5 in VS 2017