How to use TAXII & STIX in C# for threat intelligence please help how to use in C# advance thanks

STIX[^] is a serialization format based on JSON.

TAXII[^] is a transport protocol based on REST.

This means that you can take different approaches based on your particular use case. In almost all cases you can use an HttpClient-based application to query and utilize the APIs provided by whatever security partners you're trying to connect with. How you aggregate them to staff is up to you.