Это может помочь вам начать.
var manager = ExamineManager.Instance;
var searcher = manager.SearchProviderCollection["YOURSearcher"];
var query = manager.SearchProviderCollection["YOURSearcher"].CreateSearchCriteria(BooleanOperation.Or)
.Field("nodeName", keywords.Boost(10))
.Or().Field("nodeName", keywords.Fuzzy())
.Or().Field("bodyContent", keywords.Boost(5))
.Or().Field("otherField", keywords.Boost(3));
var results = searcher.Search(query.Compile());