The Object Model libraries for both Java and .NET are in sunset now. For support reasons, I recommend against the Object Model. Also, the main reason for sunsetting the Object Model was poor performance that would require significant, breaking changes to fix. So for performance reasons, I also recommend against using the Object Model.
I do recommend using our query.v1 endpoint with standard HTTP and JSON libraries. There are a number of recipes that already explain how to extract the data, including one for burndown data.
You didn't mention whether you were an on-premise or hosted customer. On-premise customers have the option of accessing a datamart using SQL.