C#JObject.Parse()怎么能等到它完全得到json字符串

本文关键字：json 字符串 C#JObject 怎么能 Parse | 更新日期: 2023-09-27 17:57:52

我只创建了一个简单的JsonDataManager，以JSON格式进行编写，并对其进行解析，以便稍后使用。然而，JObject.Parse不会等到Web客户端获得JSON数据，并直接使用"将由JSON填充"字符串。我怎样才能推送它，直到它完全得到JSON字符串？

public class JsonDataManager{
         String myData = "its going to be filled by json";

        public JsonDataManager(string Category)
        {
            String url = "<a href="http://www.kaanbarisbayrak.com/?json=get_category_posts&cat="+Category;<br">http://www.kaanbarisbayrak.com/?json=get_category_posts&cat="+Catego...</a> />
            WebClient wc = new WebClient();
            wc.Encoding = System.Text.Encoding.UTF8;
            wc.Headers["Accept"] = "application/json";
            wc.DownloadStringAsync(new Uri(url), UriKind.Relative);
            wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
        }

        public String getWriting()
        {
            JObject obj = JObject.Parse(myData);
            JArray array = (JArray)obj["posts"];
            string writing = (string)array[0]["content"]; 
            return writing;
        }

        private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            myData = e.Result;
        }

    }

C#JObject.Parse()怎么能等到它完全得到json字符串

我认为您想要使用Task<string>。这意味着getWriting()是一个最终将返回字符串但不会阻塞线程的函数。要做到这一点，只需将下载调用封装在一个任务中即可。然后，您可以附加一个ContinueWith函数作为回调函数，该函数接收结果并将其打印到屏幕上。

class JsonDataManager
{
    String url = "http://www.kaanbarisbayrak.com/?json=get_category_posts&cat=";
    string data = "";
    HttpClient hc;
    public JsonDataManager(string Category)
    {
        hc = new HttpClient();
        url += Category;
    }
    public Task<string> getWriting()
    {
        return Task.Factory.StartNew<string>(() =>
        {
            data = hc.GetStringAsync(url).Result;
            // use the resulting string
            JObject obj = JObject.Parse(data);
            JArray array = (JArray)obj["posts"];
            string writing = (string)array[0]["content"];
            return writing;
        });
    }
}

    private void Form1_Load(object sender, EventArgs e)
    {
        JsonDataManager manager = new JsonDataManager("4");
        manager.getWriting().ContinueWith((task) =>
        {
            string writing = task.Result;
            MessageBox.Show(writing);
        });
    }

您需要等待WebClient完成下载。一种方法是使用手动重置事件：

public class JsonDataManager
{
   String myData = "its going to be filled by json";
   ManualResetEvent mre = new ManualResetEvent(false);
   public JsonDataManager(string Category)
   {
       String url = "<a href="http://www.kaanbarisbayrak.com/?json=get_category_posts&cat="+Category;<br">http://www.kaanbarisbayrak.com/?json=get_category_posts&cat="+Catego...</a> />
       WebClient wc = new WebClient();
       wc.Encoding = System.Text.Encoding.UTF8;
       wc.Headers["Accept"] = "application/json";
       wc.DownloadStringAsync(new Uri(url), UriKind.Relative);
       wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
   }
   public String getWriting()
   {
       mre.WaitOne();
       JObject obj = JObject.Parse(myData);
       JArray array = (JArray)obj["posts"];
       string writing = (string)array[0]["content"]; 
       return writing;
   }
   private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
   {
       myData = e.Result;
       mre.Set();
   }
}

在此处阅读有关重置事件的更多信息。

public class JsonDataManager
{
    readonly String _url;
    public JsonDataManager(string category)
    {
        _url = @"http://www.kaanbarisbayrak.com/?json=get_category_posts&cat="+category;
    }
    public async Task<String> getWriting()
    {
        WebClient wc = new WebClient();
        wc.Encoding = System.Text.Encoding.UTF8;
        wc.Headers["Accept"] = "application/json";
        JObject obj = JObject.Parse(await wc.DownloadStringTaskAsnync(_url));
        JArray array = (JArray)obj["posts"];
        string writing = (string)array[0]["content"]; 
        return writing;
    }
}

使用它：

var jsonManager = new JsonDataManager("whatever");
var writing = await jsonManager.getWriting();

这段代码没有经过测试，但我希望你能明白。

如果您试图发布数据并获取json结果，我建议您使用StreamReader来正确获取响应。请参阅下面的方法，它将以字符串的形式返回结果，您可以将其解析为json。

公共字符串GetJsonResult（字符串url，字符串queryStringValues）{//创建web请求HttpWebRequest HttpWebRequest；httpWebRequest=（httpWebRequest）WebRequest.Create（url+queryStringValues）；httpWebRequest.Method="POST"；httpWebRequest.Timeout=6000；httpWebRequest.ContentType="application/json"；System.Net.ServicePointManager.Expect100Continue=false；//提出请求并得到回应HttpWebResponse响应=null；response=（HttpWebResponse）httpWebRequest.GetResponse（）；string content="；使用（var stream=new StreamReader（response.GetResponseStream（））{content=流。ReadToEnd（）；}退货内容；}
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