I want to add all the Records in my database in a list box (Book name), However nothing is adding to the listbox

Code:
cmd.Connection = cn
        cmd.CommandType = CommandType.Text
        cmd.CommandText = " select BookName from Book "
        rdr = cmd.ExecuteReader
        Do While rdr.Read
            cbdvuser.Items.Add(rdr.Item("BookName"))
        Loop
        cn.Close()