As I understand, you need to upload the file to the server before opening it e.g.
if (file != null && file.ContentLength > 0)
{
// extract only the fielname
var fileName = Path.GetFileName(file.FileName);
// store the file inside ~/App_Data/uploads folder
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
file.SaveAs(path);
}
I took the above from a similar question's answer by Chance and Darin Dimitrov
: File Upload ASP.NET MVC 3.0
This answer additionally references the usefull blog post Uploading a File (Or Files) With ASP.NET MVC