DropDownList in ASP.Net

Try this code on checkbox selectedindex changed event....

If(checkbox1.checked)
{
SqlCommand Cd = new SqlCommand("Select state from table name", Con);
            SqlDataReader dr = Cd.ExecuteReader();
            while (dr.Read())
            {
                dropdownlist1.Items.Add(dr["state"].ToString());
            }
SqlCommand Cd1 = new SqlCommand("Select city from table name", Con);
            SqlDataReader dr1 = Cd1.ExecuteReader();
            while (dr1.Read())
            {
                dropdownlist2.Items.Add(dr["city"].ToString());
            }
}

kindly Share your Code.......

Hi,
        Please refer the below link

http://www.codeproject.com/Articles/42247/ASP-NET-Multiple-Selection-DropDownList-with-AJAX


http://www.codeproject.com/Articles/66572/A-Multiple-Selection-DropDownList-a-CheckBoxList-I

Regards,
Iftikar

Thanks Ruchi,

But is not answer of my problem. Please read it and try again.

Use SelectionChanged event of State dropdownlist to populate items in City dropdownlist.