C# file IO and impersonation Issues

I have an app that needs to connect to a share on a NAS device and do some disk IO (Reading and writing out PDF documents)

I made a virtual directory in IIS that is working correctly (can access the files, etc).

I can not use the web.config

<identity impersonate="true" userName="user" password="password"/>

for impersonation, as most of the application needs to run as the default ASPNET user.

I made a test site using the above impersonation and it works fine (clears auth and can read/write files fine)

I went back and tried to implement a code based solution for an on demand impersonation and end up with the error:
Access to the path "\\NasDevice\Share\Doc_I_Am_Saving.pdf" is denied.


I am not exactly sure why, as I am outputting the current login, and it looks correct, its switching from NETWORK SERVICE to the impersonated account and back.

Here is the code snippit related to the task:

IntPtr lnToken;
int TResult =LogonUser("Account",".","Password",LOGON32_LOGON_NETWORK,LOGON32_PROVIDER_DEFAULT,out lnToken);

if ( TResult > 0 )
{
      ImpersonateLoggedOnUser(lnToken);
      StringBuilder sb = new StringBuilder(80,80);
      uint Size = 79;
      Response.Write(Page.User.Identity + " - " + System.Security.Principal.WindowsIdentity.GetCurrent() + " - " +       System.Threading.Thread.CurrentPrincipal.Identity);
      Response.Write( Environment.UserName + " - " + this.User.Identity.Name + "<hr>");
      string fn = System.IO.Path.GetFileName(File1.PostedFile.FileName);
      string SaveLocation = Server.MapPath("/PDF") + "\\" +  fn;
      
      try
      {
            File1.PostedFile.SaveAs(SaveLocation);
            Response.Write("The file has been uploaded." + SaveLocation);
      }
      catch ( Exception ex )
      {
            Response.Write("Error: " + ex.Message);
      }
      RevertToSelf();
      Response.Write("<hr>" + Environment.UserName); CloseHandle(lnToken);
}
else { Response.Write("Not logged on: " + Environment.UserName); } Start Free Trial