Removes all fields with the given name from the document. If there is no field with the specified name, the document remains unchanged.
Note that the removeField(s) methods like the add method only make sense prior to adding a document to an index. These methods cannot be used to change the content of an existing index! In order to achieve this, a document has to be deleted from an index and a new changed version of that document has to be added.
Document Class | Lucene.Net.Documents Namespace