1 . 
using (SqlConnection con = new SqlConnection(connectionString))
                {
                command = new SqlCommand("dbo.get_data");
                    command.Connection = con.Connection;
                command.CommandType = CommandType.StoredProcedure;
///...
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    if (!reader.HasRows)
                    {
                        return null;
                    }

                    while (reader.Read())
                    {
...
                    }
                 }
                }

 2 . 
SqlConnection oConn = new SqlConnection(); 
     DataTable oTable = new DataTable(); 
         
     try 
     {   
       oConn.ConnectionString =  "connection string";
       oConn.Open();       
       SqlDataAdapter oDA = new SqlDataAdapter("exec get_data",oConn); 
       oDA.Fill(oTable); 
       oConn.Close(); 
     } 
     catch (Exception e) {   }   
     finally{ if (oConn.State == ConnectionState.Open) { oConn.Close(); } } 

     // To Iterate Through Rows

     foreach(DataRow oRow in oTable.Rows) 
     {  
       Response.Write(oRow["username"].ToString()); 
     } 

myob.Name = r["name"].ToString();
myob.LengthSm = r["lensm"].ToString();
...

private static DataSet SelectRows(DataSet dataset,
    string connectionString,string queryString) 
{
    using (SqlConnection connection = 
        new SqlConnection(connectionString))
    {
        SqlDataAdapter adapter = new SqlDataAdapter();
        adapter.SelectCommand = new SqlCommand(
            queryString, connection);
        adapter.Fill(dataset);
        return dataset;
    }
}

//  1         
        private DataSet SelectRows(DataSet dataset,
            string connectionString, string queryString)
        {
            using (SqlConnection connection =
                new SqlConnection(connectionString))
            {
                SqlDataAdapter adapter = new SqlDataAdapter();
                adapter.SelectCommand = new SqlCommand(
                    queryString, connection);
                adapter.Fill(dataset);
                return dataset;
            }
        }
//  2 
        private DataTable SelectRows(DataTable datatable,
            string connectionString, string queryString)
        {
            using (SqlConnection connection =
                new SqlConnection(connectionString))
            {
                SqlDataAdapter adapter = new SqlDataAdapter();
                adapter.SelectCommand = new SqlCommand(
                    queryString, connection);
                adapter.Fill(datatable);
                return datatable;
            }
        }
//  3  
        private static List<Guid> SelectRowsReader(string connectionString, string queryString)
        {
            List<Guid> nodeList = new List<Guid>( 100000 );
            using (SqlConnection connection =
                new SqlConnection(connectionString))
            {
                connection.Open();
                SqlCommand command = new SqlCommand(queryString);
                command.Connection = connection;
                command.CommandType = CommandType.Text;
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    if (!reader.HasRows)
                    {
                        return null;
                    }
                    while (reader.Read())
                    {
                        Guid guid = new Guid(reader["id"].ToString());
                        nodeList.Add(guid);
                    }
                }
                return nodeList;
            }
        }