how to display value from database in drop down list asp.net

DataTable dt = new DataTable();
               string connectionString = "your connetion string";
               SqlConnection con = new SqlConnection(connectionString);
               SqlDataAdapter adapter = new SqlDataAdapter("SELECT DisplayNameColumn,ValueNameColumn FROM TableName", con);
               adapter.Fill(dt);
               DropDownList1.DataTextField = "DisplayNameColumn";
               DropDownList1.DataValueField = "ValueNameColumn";
               DropDownList1.DataSource = dt;
               DropDownList1.DataBind();