Rellenar un ComboBox con un DataReader

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;
 
//...
SqlConnection con = null;
SqlCommand command = null;
String cs = "cadena de conexión SQL";
SqlDataReader dr = null;
 
try
{
   con = new SqlConnection(cs);
   command = new SqlCommand("SELECT campo FROM Tabla", con);
   con.Open();
   dr = command.ExecuteReader();
 
   ComboBox1.Items.Clear();
 
   if(dr.HasRows)
   {
     while(dr.Read())
     { ComboBox1.Items.Add(dr.GetValue(0));}
   }
   else
   { MessageBox.Show("No result for your Data", "Infos", 
MessageBoxButtons.OK, MessageBoxIcon.Information);}
}
catch(Exception ex)
{ MessageBox.Show(ex.Message);}
finally
{
   if(dr != null) {dr.Close();}
   if(con != null) {con.Close();}
}