For a social media messaging app that must identify the language of text messages in real time, the most direct SDK is the Azure AI Translator - Text Translation SDK. Its client libraries (e.g., Azure.AI.Translation.
Text in .NET) include a language detection operation that returns the detected language code and a confidence score, which is exactly what you need for real-time text scenarios.
Other options are not a fit:
Microsoft.CognitiveServices.Speech is the Speech SDK for speech-to-text, TTS, and speech translation (audio), not text-only language detection.
Azure.AI.Translation.Document targets asynchronous document translation workflows, not short text message detection. Microsoft Learn Azure.AI.Translation.Speech isn't the package used; speech translation is covered by the Speech SDK package above. Microsoft Learn Microsoft References Text Translation SDK overview (supports language detection): Azure AI Translator. Microsoft Learn DetectedLanguage in Azure.AI.Translation.Text (returned by detect operation). Microsoft Learn Quickstart: Translator text client libraries. Microsoft Learn Install/use the Speech SDK (contrast with text scenario). Microsoft Learn Document Translation SDK overview (not applicable to short text detection). Microsoft Learn