SubDirectory is created, but file doesn't upload

I have a vb.net page with three upload fields.  When the user clicks submit, I want to upload all three files into a specific directory with a subdirectory dynamically named based upon a value.  The code below creates the subdirectory with a value equal to hdnMatterid.Value, BUT, doesn't upload the file, and doesn't throw any error.    What am I doing wrong? 

Dim d As New System.IO.DirectoryInfo("C:\xxx\wwwroot\Intranet\ExternalApps\yyy")
d.CreateSubdirectory(hdnMatterID.Value)
Dim uploadedFiles As HttpFileCollection = Http ...