use gridview1.DataBind(); again to show the changes . as
string strup = "Update FileRequest set FileStatus='1' where id=@id";
SqlCommand cmdup = new SqlCommand(strup,Db.GetConnection());
cmdup.Parameters.AddWithValue("id",Int32.Parse(lblReqID.Text));
cmdup.ExecuteNonQuery();
GridView1.DataBind();