Show HN: Open-Source C# Library to Extract Structured Data from OpenAI API

Historically, we've done a lot of OCR work with mixed results in the .NET ecosystem. There were always a lot of tradeoffs. We were super excited when the GPT4V was announced, and quickly saw a lot of potential for data extraction from images. There are a few pitfalls though. Primarily, GPT4V does not currently support tooling (i.e. function calling) and you cannot specify that you expect a JSON result in the API call.

...set aside the fact that good OpenAI libraries for .NET are hard to come by...

After looking over the way function calling works in completions, we realized we could do the same basic thing against GPT4V. Essentially, we annotate a simple class with a few attribtutes to instruct the API in what we want to accomplish. Then, we convert the object into a JSON schema specification and pass that in the prompt.

This has worked pretty well for us, and we've used it in a number of client projects. While I am sure that OpenAI will eventually support all of this directly through the API, I hope that some of our .NET brethren find it useful in the meantime!

The library is distributed via nuget, and the GitHub repo includes the library code as well as a simple demo app to check out the functionality locally.