how to create writable and searchable dropdown list in my asp.net usin c#

i think thier is no writable ddl up to my knowledge....

but i will explain about the searchable dropdownlist...
First type....

when u took ddl from toolbox to form or webpage..just simply select it and go to the properties page... their u can find "combobox/drop down list" in tools... then simply rag it on to ur place...then go to the propertis their u can find items collection click on it n add ur items their what to want to see in ur dropdownlist.....
like
country: usa,uk,india like that

Second type....

serachable ddl menas u want to drop all the table content series to the ddl then simply use the below code:

con.Open();
SqlCommand cmd = new SqlCommand("select * from StateTable where CountryID="+CountryID, con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
con.Close();
ddlState.DataSource = ds;
ddlState.DataTextField = "StateName";
ddlState.DataValueField = "StateID";
ddlState.DataBind();
ddlState.Items.Insert(0, new ListItem("--Select--", "0"));
if(ddlState.SelectedValue=="0")
{
ddlRegion.Items.Clear();
ddlRegion.Items.Insert(0, new ListItem("--Select--", "0"));
}