c# - JsonConvert.DeserializeObject throw exception when retrieving JSON from Rest API -

i have issue cannot solve. have nodejs server can send simple json through rest api.

var filename = 'latestversion.json'; fs.readfile(filename, 'utf8', function (err, data) {      if (err) throw err;              filejson = json.parse(data.tostring('utf8').replace(/^\ufeff/, ''));      res.json(data); }); 

i retrieve json in c# application:

class appversion {    public int major { get; set; }    public int minor { get; set; }    public int build { get; set; } }  httpwebrequest http = (httpwebrequest)httpwebrequest.create(new uri(url)); httpwebresponse response = (httpwebresponse)http.getresponse(); string versionstring = null; using(system.io.streamreader sr = new system.io.streamreader(response.getresponsestream())) {    versionstring = sr.readtoend(); } if(versionstring != null) {    appversion test = new appversion() { major = 1, minor = 1, build = 1 };    string teststr = jsonconvert.serializeobject(test);    var j = jsonconvert.deserializeobject<appversion>(versionstring); } 

i have exception "cannot cast or convert...." when deserializing. however, if use teststr goes well. looked @ strings , found :

teststr = "{\"major\":1,\"minor\":1,\"build\":1}" versionstring = "\"{\\\"major\\\": 1, \\\"minor\\\": 1, \\\"build\\\": 1}\"" 

more strange, tried edit versionstring hand removing escape characters , got still error (the json visualizer says badly formatted).

any clue solve ?