在这行代码上:
var arr = JsonConvert.DeserializeObject<JArray>(s);
我得到了,">无法强制转换类型为"Newtonsoft"的对象。Json。林克。JObject"to type"Newtonsoft。Json。林克。J阵列'">
我把那行改成了这个:
JArray arr = JsonConvert.DeserializeObject<JArray>(s);
并且得到了相同的错误消息。
我把它改成这个:
var arr = JsonConvert.DeserializeObject<JObject>(s);
它甚至无法编译。
此时调用读取的值(字符串s(为:
{"id":347745,"results":[{"iso_3166_1":"US","release_dates":[{"certification":"","iso_639_1":"","note":"","release_date":"1936-12-12T00:00:00.000Z","type":3}]}]}
我想要的只是";"认证";;在这种情况下,证明值是空字符串("证明":"(
在上下文中,代码是:
. . .
try
{
var webRequest = (HttpWebRequest)WebRequest.Create(RESTStringToGetMPAARatingForMovieId);
webRequest.Method = "GET";
var webResponse = (HttpWebResponse)webRequest.GetResponse();
if ((webResponse.StatusCode == HttpStatusCode.OK) && (webResponse.ContentLength > 0))
{
StreamReader streamReader = new StreamReader(webResponse.GetResponseStream());
string s = streamReader.ReadToEnd();
var arr = JsonConvert.DeserializeObject<JArray>(s);
//JArray arr = JsonConvert.DeserializeObject<JArray>(s);
//var arr = JsonConvert.DeserializeObject<JObject>(s);
foreach (JObject obj in arr)
{
_currentMPAARating = (string)obj["certification"];
. . .
}
}
else
{
MessageBox.Show(string.Format("Status code == {0}, Content length == {1}",
webResponse.StatusCode, webResponse.ContentLength));
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
您的JSON不是数组,它是一个包含数组(results
(的对象。但实际上它比这更复杂:您要查找的certification
字符串嵌套在第二个release_dates
数组中。
如果您获取JSON并使用JSON验证器/美化程序对其进行重新格式化,它应该会变得更加清晰:
{
"id": 347745,
"results": [
{
"iso_3166_1": "US",
"release_dates": [
{
"certification": "",
"iso_639_1": "",
"note": "",
"release_date": "1936-12-12T00:00:00Z",
"type": 3
}
]
}
]
}
因此,要使用常规的foreach
循环获得您正在寻找的数据,您需要这样的代码:
var obj = JsonConvert.DeserializeObject<JObject>(s);
var resultArr = (JArray)obj["results"];
foreach (JObject resultObj in resultArr)
{
var releaseDatesArr = (JArray)resultObj["release_dates"];
foreach (JObject releaseDateObj in releaseDatesArr)
{
_currentMPAARating = (string)releaseDateObj["certification"];
// ...
}
}
Fiddle:https://dotnetfiddle.net/SMzQTw
如果你只需要一个项目,这里有一个快捷方式。使用带有递归下降算子(..
(的SelectToken
方法,如下所示:
var obj = JsonConvert.DeserializeObject<JObject>(s);
_currentMPAARating = (string)obj.SelectToken("..certification");
Fiddle:https://dotnetfiddle.net/S1ScLO
但请注意,以上内容只会返回第一场比赛。如果您希望获得多个证书,您可以使用SelectTokens
(复数(:
var obj = JsonConvert.DeserializeObject<JObject>(s);
var ratings = obj.SelectTokens("..certification").Select(t => (string)t).ToList();
Fiddle:https://dotnetfiddle.net/zyjNnJ