Dictionary<string, string> droplistds= new Dictionary<string, string>();
droplistds.Add("1", "China");
droplistds.Add("2", "USA");
droplistds.Add("3", "Canada");
droplistds.Add("4", "Japan");
dropdownlist1.DataSource = droplistds;
dropdownlist1.DataValueField = "Key";
dropdownlist1.DataTextField = "Value";
dropdownlist1.DataBind();