How to put --select one-- or choose one in dropdownlist in asp.net using C#

In this article show how to add --select one-- or --choose one-- on the top of dropdownlist in asp.net using C#. I already post how to binding data in to dropdownlist from database in asp.net using C#.
 Code design:

<asp:DropDownList ID="Dropdownlist1" runat="server" Height="20px" Width="220px" AppendDataBoundItems="true">

   <asp:ListItem Value="-1" Text="-- All project--" Selected="true">
   </asp:ListItem>

</asp:DropDownList>

After design code dropdownlist, it's time to binding data to dropdownlist. See how to binding data into dropdownlist.

Note : -  AppendDataBoundItems="true" mean enable append items to dropdownlist.

          -  Value="-1": put the value is -1 because data binding from database, which value is started from 0.