How to add an item to DropDownList after databind in dropdownlist add item after databind
The following c# example code demonstrate us how can we add an item to DropDownList server control after data bind. We can populate a DropDownList programmatically at run time by data binding with various data sources such as Array, SqlDataSource, ObjectDataSource etc. We only need to specify the DropDownList DataSource and after that call the DataBind() method.

After data binding a DropDownList control we can add or insert an item to its items collection. In this example code we uses items collection Insert() method to add an item to DropDownList. Insert() method allow us to insert an item to DropDownList at any index position because it has a required parameter to pass index value.

<%@ Page Language="C#" AutoEventWireup="true"%>  
<!DOCTYPE html>
<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
        if (!Page.IsPostBack)
            string[] birds = { "King Penguin", "Gentoo Penguin", "Adelie Penguin", "Fairy Penguin" };
            DropDownList1.DataSource = birds;
            ListItem li = new ListItem();
            li.Text = "Wandering Albatross";
            li.Value = "6";

            //this line add list item at list top after data bind.
            DropDownList1.Items.Insert(0, li);
<html xmlns="">      
<head id="Head1" runat="server">      
    <title> dropdownlist add item after databind</title>
    <form id="form1" runat="server">      
        <h2 style="color:MidnightBlue; font-style:italic;">      
   example - dropdownlist add item after databind
        <hr width="550" align="left" color="Gainsboro" />      
        <br /><br />
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