Adding Dropdownlist Option after databinding

Hi I have a dropdownlist (ddl2) which is dependent on the selected value of another dropdownlist (ddl1).
I have set the appendatabounditems to "true" for ddl2 and have added a "Please Select" and a "Select All" options.  The Options show in the list when the page first loads. 
When ddl1 is selected the page refreshes and ddl2 is populated, however the "Please Select" and "Select All" options have disappeared.
How can I keep these extra options in ddl2?
 
Thanks for your help,
Fiorano
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