tokens: You have just to remove this line from your code : string myString = reader.ReadAsString() ; The Json Serializer tries to read a string there , but recognizes that it is an Array which you 're trying to read .
ner_tags: O O O O O O O O O O O B-Code_Block I-Code_Block I-Code_Block I-Code_Block I-Code_Block O B-Class I-Class O O O O B-Data_Type O O O O O O O O B-Data_Structure O O O O O O O