Adding Guid

Question

I need to add GUID for each photos that users had uploaded. I had created a virtual directory in IIS to store the images that users had uploaded.
The coding is
string strImage = "";
if (!File.Exists) (Server.MapPath("D:/Virtual Directory")));
if(FileUpload1.HasFile)
{
  strImage = FileUpload1.FileName.ToString();
  FileUpload1.SaveAs (Server.MapPath("D:/Virtual Directory/" + FileUpload1.FileName.ToString()));
}


//produces a "blank GUID"
System.Guid blankGuid = new System.Guid();
//produces a new, unique GUID
System.Guid desiredGuid = System.Guid.NewGuid();


Can someone tell me how to link them together?