file name issue

I've the following code:
string FileName = GetFileNameFromPath(this.TreeView1.SelectedNode.ValuePath);


            FileInfo fi = new FileInfo(this.TreeView1.SelectedNode.Value.ToString());
           
            Response.Clear();

            Response.AddHeader("Content-Disposition", "attachment; filename=" + FileName);
            Response.AddHeader("Content-Length", fi.Length.ToString());
            Response.ContentType = "application/msword";
            Response.TransmitFile(FileName);
 & ...