Generic async method for reading all db rows in c# #csharp

GetAllRowsAsync.cs

protected async Task<IEnumerable<T>> GetAllRowsAsync<T>(DbConnection conn, string query, Func<DbDataReader, Task<T>> asyncMapper, CancellationToken token)
  where T : class
{
  IList<T> result = new List<T>();

  using (conn)
  using (var cmd = conn.CreateCommand())
  {
    await conn.OpenAsync(token);
    cmd.CommandText = query;
    using (var reader = await cmd.ExecuteReaderAsync(token))
    {
      while (await reader.ReadAsync(token))
      {
        T mappedObj = await asyncMapper(reader);
        if(mappedObj != null)
        {
          result.Add(mappedObj);
        }
      }
    }
  }

  return result;
}

Usage.cs

private const string query = @"SELECT * FROM Sth";

public async Task<IEnumerable<SthEntry>> GetSthAsync(CancellationToken token)
{
  return await GetAllRowsAsync(new SqlConnection(connectionString), query, async (reader) =>
  {
    return new SthEntry
    {
      Id = reader.GetInt32(0),
      Name = reader.GetString(1),
      Email = (!await reader.IsDBNullAsync(3)) ? reader.GetString(3) : string.Empty,
    };
  }, token);
}