protected void uploadFile()
    {
        String projectID = (String)Session["projId"];
        //change the file name
        if (!FileUpload.FileName.Equals(""))
        {
            // Create a new folder in Docs folder (folder name = projectID)
            System.IO.Directory.CreateDirectory(Server.MapPath("Docs/") + projectID);
 
            // Save the file into the new folder.
            FileUpload.PostedFile.SaveAs(Server.MapPath("Docs/" + projectID + "/" + FileUpload.FileName));
            lblFile.Text = FileUpload.FileName + " is uploaded!";
            lblFile.Visible = true;
 
        }
    }//end of method

protected void btnLink_OnClientClick(object sender, EventArgs e)
{
   String projectID = (String)Session["projId"];
   String file1 = System.IO.Path.GetFileName(Server.MapPath("Docs/" + pid + "/"));
}

FileInfo finfo = new FileInfo(Server.MapPath(MyFile));
long FileInBytes = finfo.Length;

DirectoryInfo diSource = new DirectoryInfo(Server.MapPath("Docs/" + pid + "/EP/"));
        string ExactFilename = string.Empty;
 
        foreach (FileInfo file in diSource.GetFiles(@"*.*"))
        {
            ExactFilename = file.FullName;
        }      
        System.Diagnostics.Process.Start(ExactFilename);