the result of the query inserted in an array/list with distinction of 2 columns.?

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C#

VB

SQL-Server

Visual-Studio

, +

ex.
A 01/01/2011
B 01/01/2011
C 01/01/2011
D 01/01/2011
A 01/02/2011
B 01/02/2011
D 01/02/2011
A 01/03/2011
D 01/03/2011

The query were planning to use ?

SELECT DISTINCT Alphabets, dateReceive FROM
database
ORDER BY Alphabets

using List<string>

Our expected output
[{A,B,C,D},{A,B,D},{A,D}

using (var conn = new SqlConnection("Data Source=SERV-PC\\MSQLSERVER;Initial Catalog=MyDatabase;Integrated Security=True"))
            {
                using (var cmd = new SqlCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText = "SELECT DISTINCT [ColumnA], [DateReceive] FROM [MyDatabase].[dbo].[dummy] WHERE [ColumnA]=@loca  AND [DateReceive] BETWEEN '01/01/2013' and '01/07/2013' ";
                    cmd.Parameters.AddWithValue("@loca", DropDownList1.SelectedValue.ToString());
                    conn.Open();

                    using (var reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            var tmp = reader["ColumnA"];
                            if (tmp != DBNull.Value)
                            {
                                ListBox1.Items.Add(reader["ColumnA"].ToString());
                            }
                        }
                    }
                }
            }