Are you looking for a full-text search API that allows you to search over a lot of document formats? In that case, GroupDocs.Search for .NET will meet your requirements. API creates index and then perform instant search across thousands of documents.
Those who are already working with the API, we have some new features and improvements. Moreover, some classes have been renamed to improve code readability. There are minor changes in the new version 19....fragments Enhance document metadata indexing with new formats...terms: How to enhance document metadata indexing with new formats...