clickhouse c#查询 ExecuteReader

using (var cnn = GetConnection(connStr))
{

var cmd = cnn.CreateCommand("SELECT DISTINCT ReceiverMobile from crm.Tag_Teacher limit 20000");

var dr=cmd.ExecuteReader();
do
{
while (dr.Read())
{
string str = dr[0].ToString();

}
}
while (dr.NextResult());
dr.Close();


}