How can I translate VB6 Recordset.FindFirst to C# while using an Access Database?

Question

I'm working on a project where I'm converting an old VB6 project to .NET/C#. I've come upon a method that performs several queries, once of which uses the recordset.FindFirst method to generate sub-results. I'm at a loss on how to translate this into C# without using LINQ (something I have no experience with anyway). I've search through Google, etc and cannot find a relevant example that doesn't use LINQ. Can anyone provide me with a simple C# example that executes a query, then executes a sub-clause against those results without using LINQ?

In my code I am using an OldDbConnection and an OleDbReader to query the table from the Access database. Perhaps this is wrong?

Many thanks in advance for any examples you can provide.

Answer 1

One way to do it would be to load the initial query results into a DataTable and then use the .Select method to run the secondary query against the initial results. For example, for a table named [Users] in Access containing...

ID  UserName
--  --------
1   Jeff
2   Greg
3   Garth
4   Gord
5   Gary
6   Grant
7   Graham

...the following C# code...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;

namespace oledbTest1
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var conn = new OleDbConnection())
            {
                conn.ConnectionString =
                        @"Provider=Microsoft.ACE.OLEDB.12.0;" +
                        @"Data Source=C:\__tmp\testData.accdb;";
                conn.Open();
                using (var cmd = new OleDbCommand())
                {
                    cmd.Connection = conn;
                    cmd.CommandText =
                        "SELECT * FROM Users WHERE ID < 7 ORDER BY UserName";
                    var da = new OleDbDataAdapter(cmd);
                    var dt = new System.Data.DataTable();
                    da.Fill(dt);
                    Console.WriteLine("The initial query from the Access database (WHERE ID < 7) returned:");
                    foreach (System.Data.DataRow dr in dt.Rows)
                    {
                        Console.WriteLine(dr["UserName"]);
                    }
                    System.Data.DataRow[] subsetRows;
                    subsetRows = dt.Select("UserName LIKE 'Gr%'");
                    Console.WriteLine();
                    Console.WriteLine("The equivalent of \".FindFirst UserName LIKE 'Gr%'\" on that subset would be:");
                    Console.WriteLine(subsetRows[0]["UserName"]);
                }
                conn.Close();
            }
        }
    }
}

...produces the following result:

The initial query from the Access database (WHERE ID < 7) returned:
Garth
Gary
Gord
Grant
Greg
Jeff

The equivalent of ".FindFirst UserName LIKE 'Gr%'" on that subset would be:
Grant