Question

I have the following class which I am using to read in large amounts of data from an Access database.

public class ConnectToAccess
{
    private readonly string _connectionString;

    public ConnectToAccess(String connectionString)
    {
        _connectionString = connectionString;
    }

    public List<String> GetData(String sql)
    {
        var data = new List<String>();
        using (var connection = new OleDbConnection(_connectionString))
        {
            using (var command = connection.CreateCommand())
            {
                command.CommandText = sql;
                command.CommandType = CommandType.Text;
                connection.Open();
                using (var reader = command.ExecuteReader())
                {
                    if (reader != null && reader.HasRows)
                    while (reader.Read())
                    {
                        data.Add(reader["First Name"] + " " + reader["Last Name"]);
                    }
                }
            }
        }
        return data;
    }
}

As is, this code is working and is successfully pulling data in from the database. However, I would like to enhance the GetData() method to make it more dynamic. I would like it to somehow return a list of anonymous objects, where each object has properties relating to the columns of the dataset returned.

I’ve been coding in .Net for a while, but I’m still rather new at many concepts. I’m not quite sure how to create this list of anonymous objects that mirror the columns in the dataset most effectively. I’m also not sure what return type I would use in this case, I’m thinking maybe List. Then I suppose I would need to use reflection to pull the data out of those anonymous objects and transfer it into where it needs to go.

If anyone can help me with any significant part of this puzzle, I would be most obliged.

Answer 1

You can’t have an anonymous type as a return type.
Why not just return a DataTable. You can even use a DataAdapter to make the process a lot easier. It also gets you the schema.

If you insist on getting objects for everything:

public IEnumerable<T> GetData(String sql, Func<DataReader, T> selector)
{
    //code elided

    while (reader.Read())
    {
        yield return selector(reader);
    }    
}

Now you can use it with a selector:

var people = GetData("Select * from People", reader => new Person { Name = reader{"Name"], Age = reader["Age"] })
people.Take(5); //first five records only