A Generic Database Reader Class

I’ve been doing a lot of CRUD-type work recently against a reporting database.  The application does not utilize an ORM because of the complexity of selection SQL, so I’ve been designing a custom ORM framework.

One of my top priorities is to route all database access through a single class, so I developed this generic database reader.  The code is shown below.

The generic reader class is DataReaderHelper.  It has a GetData generic method that accepts a generic delegate and returns read data using a referenced generic parameter.  This combination of generics and delegates provides an exceptionally flexible class that I can use for any database reads, ensuring that my connections are centrally managed.

The code sample below also provides sample usage in the Mapper class.

// generic class for reading database data
public class DataReaderHelper
{
    // generic delegate passed into the GetData method to manipulate the IDataReader object
    public delegate void ReadDatabaseValue<T>(IDataReader reader, ref T businessObject);
    // delegate is passed into the GetData method to create a new connection
    public delegate IDbConnection CreateConnection();

    public static void GetData<T>(CreateConnection createConnection, string sql, 
        ReadDatabaseValue<T> readDelegate, ref T businessObject)
    {
        IDbConnection dbConnection = null;
        IDbCommand command = null;
        IDataReader reader = null;
        try
        {
            dbConnection = createConnection();
            if (dbConnection.State != ConnectionState.Open) { dbConnection.Open(); }
            command = dbConnection.CreateCommand();
            command.CommandText = sql;
            reader = command.ExecuteReader();
            while (reader.Read())
            {
                readDelegate(reader, ref businessObject);
            }
        }
        catch { throw; }
        finally
        {
            if (dbConnection != null) dbConnection.Dispose();
            if (command != null) command.Dispose();
            if (reader != null) reader.Dispose();
        }
    }
}

// provides the database connection delegate
internal class ConnectionFactory
{
    internal static SqlConnection GetConnection()
    {
        try
        {
            return new SqlConnection(ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString);
        }
        catch { throw; }
    }
}

// provides delegates used to read data
internal class DataReaderFactory
{
    internal static void ReadFirstColumnIntoString(IDataReader reader, ref string value)
    {
        value = reader.GetString(0);
    }
    internal static void ReadFirstColumnIntoStringCollection(IDataReader reader,
        ref StringCollection value)
    {
        value.Add(reader.GetString(0));
    }
}

// example DataReaderHelper usage
internal class Mapper
{
    internal static string DemoGetString()
    {
        string demo = null;
        DataReaderHelper.GetData<string>(ConnectionFactory.GetConnection, "my sql",
            DataReaderFactory.ReadFirstColumnAsValue, ref demo);
        return demo;
    }

    internal static StringCollection DemoGetStringCollection()
    {
        StringCollection demo = null;
        DataReaderHelper.GetData<StringCollection>(ConnectionFactory.GetConnection, "my sql",
            DataReaderFactory.ReadFirstColumnAsInt32IdList, ref demo);
        return demo;
    }
}