Microsoft Cognitive Services
In order to run Version 2 code below, you first need to sign up for this service, and then use the account keys provided in the programs below. Sentiment, key phrases and topics APIs currently only support English language text. Support for other languages coming soon.

Key phrases, Language, Sentiment APIs (up to 1000 records)
Topic Detection API (at least 100 records)
Key phrases, Language, Sentiment APIs (up to 1000 records)
Topic Detection API (at least 100 records)
The code below requires the popular JSON library Json.NET. It is available for free here.
Single record API
Batch API (up to 1000 records)
Topic Detection API (at least 100 records)
Single record API
Batch API (up to 1000 records)
Topic Detection API (at least 100 records)