How to delete a particular item from a drop down

Sandeep Mewara is right.There are two Drop down list

I have done it using First method. the code is like this at aspx page

<asp:dropdownlist id="ddl1" runat="server" autopostback="True" onselectedindexchanged="ddl1_SelectedIndexChanged" xmlns:asp="#unknown">
   <asp:listitem>A</asp:listitem>
   <asp:listitem>B</asp:listitem>
   <asp:listitem>C</asp:listitem>
   <asp:listitem>D</asp:listitem>
   <asp:listitem>E</asp:listitem>
</asp:dropdownlist>
                
<td>
   <asp:dropdownlist id="ddl2" runat="server" xmlns:asp="#unknown">
      <asp:listitem>A</asp:listitem>
      <asp:listitem>B</asp:listitem>
      <asp:listitem>C</asp:listitem>
      <asp:listitem>D</asp:listitem>
      <asp:listitem>E</asp:listitem>
   </asp:dropdownlist>
</td>

At aspx.cs page

protected void ddl1_SelectedIndexChanged(object sender, EventArgs e)
{
    ddl2.Items.Remove(ddl1.SelectedItem);
}

You can enhance the code according to your desired need

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