Return IEnumerable from a database query....

EnumerableRepository.cs

//Note: this was pretty much an acedemic exercise... I don't recommend using this pattern.  IObservable would be much better suited.
class SomeRepository : IDisposable
    {
        private const string sql = "select * from sometable;";
        private const string connString = @"Data Source=LOCALHOST\SQLEXPRESS;Initial Catalog=sandbox;Integrated Security=SSPI;";

        public void Dispose()
        {
            if (reader != null) reader.Dispose();
            if (connection != null) connection.Dispose();
            connection = null;
        }

        private SqlConnection connection;
        private SqlDataReader reader;
        private bool rowExists = true;

        public async Task<IEnumerable<Task>> RunQuery(Func<UserDataModel, Task> doThisForEachRow)
        {
            if (connection != null) throw new InvalidOperationException("A query is already in progress. Create a new object to run another query.");
            connection = new SqlConnection(connString);
            await connection.OpenAsync();
            var command = new SqlCommand(sql, connection);
            reader = await command.ExecuteReaderAsync();
            if (!reader.Read())
            {
                return Enumerable.Empty<Task>();
            }
            return GetTasks(doThisForEachRow);
        }

        public IEnumerable<Task> GetTasks(Func<UserDataModel, Task> doThisForEachRow)
        {
            //this is the hackiest thing ever...
            while (rowExists)
            {
                yield return GetData(doThisForEachRow);
            }
        }

        private async Task GetData(Func<UserDataModel, Task> doThisForEachRow)
        {
            var model = new dataModel((string) reader["column1"], (string) reader["column2"]);
            await doThisForEachRow(model);
            rowExists = await reader.ReadAsync();
        }
    }