How to use dropdown option in HTML using ASP.NET?

no sir..iam new user...
i am designing webform..

at the backend i used...
protected void loadapprove()
{
string connectionString = ConfigurationManager.ConnectionStrings["ConnectionISG_Trainee"].ConnectionString;
using (OracleConnection connection = new OracleConnection())
{
connection.ConnectionString = connectionString;
connection.Open();
Console.WriteLine("State: {0}", connection.State);
Console.WriteLine("ConnectionString: {0}", connection.ConnectionString);
OracleCommand command1 = connection.CreateCommand();

string staff = "select per_empcode, per_empname||'-'||per_empcode staffno from adm.edbdpersonnel order by per_empname";

OracleDataAdapter adap1 = new OracleDataAdapter(staff, connection);

DataTable ds1 = new DataTable();

adap1.Fill(ds1);
dd_approve.DataSource = ds1;
dd_approve.DataTextField = "staffno";
dd_approve.DataValueField = "per_empcode";
dd_approve.DataBind();
dd_approve.Items.Insert(0, new ListItem("--Select--", ""));




connection.Close();
}
}
this code works....but since i have 300 name list , it is difficult to select the name..