Rename file while uploading file in specific folder

Hi…

I want to rename my file name that while I am uploading file in my files folder. Which  changes should I do in below code?. New name should be pick from text box.

protected void Upload_Click(object sender, EventArgs e)
   {
       String strFilename = Path.GetFileName(FileUpload1.FileName);
       String StrFilePathName = String.Empty;
       String strBaseDir = AppDomain.CurrentDomain.BaseDirectory + "Files";
 if (!Directory.Exists(strBaseDir))
       {
           Directory.CreateDirectory(strBaseDir);
       }
       StrFilePathName = strBaseDir + "\\" + strFilename;
       FileUpload1.SaveAs(StrFilePathName);
       if (!FileUpload1.HasFile) return;
       Response.Redirect("~/Default2.aspx");
   }