How to remove Dropdown values in asp.net using c sharp?

Question

i have  one dropdown in my form .....

 if we click dropdown and it shows vales like 1
                                                             2
     3 
     4  etc

  I select value (1) in dropdown and saved those values in table successfully.

   i need to remove the selected value(1) from dropdown after saved those values in table ....

   If we click the dropdown again....I need the below result.....
   
   I need result like    2
    3
     4


   value 1 have to remove from the  dropdown...How?