解析JSON时出现NullReferenceException

当有人单击按钮时，我试图解析一个JSON文件，它用JSON中的数据替换按钮的内容

目前我面临一个数据仍然为空的问题。代码如下：

private void Button1_Tap(object sender, System.Windows.Input.GestureEventArgs e)
    {
        Button1.FontSize = 15;
        Button1.Content = "Fetching...";
        var client = new WebClient();
        client.OpenReadCompleted +=
            (s, eargs) =>
            {
                var serializer = new DataContractJsonSerializer(typeof(RadioRootObject));
                if (eargs.Error != null)
                {
                    if (eargs.Error.Message.Contains("NotFound"))
                    {
                        MessageBox.Show("Could not retrieve playlist", "Error", MessageBoxButton.OK);
                        Button1.Content = "Could not retrieve playlist";
                    }
                    else
                    {
                        MessageBox.Show("Could not retrieve playlist", "Error", MessageBoxButton.OK);
                        Button1.Content = "Could not retrieve playlist";
                    }
                }
                else
                {
                    var root = (RadioRootObject)serializer.ReadObject(eargs.Result);
                    var songHistory = root.station3;
                    Button1.Content = songHistory.text;
                }
            };
        var uri = new Uri("http://www.reignofcomputer.com/tmpsend/nowplaying.json");
        client.OpenReadAsync(uri);
    }

    public class station1
    {
        public string station { get; set; }
        public string title { get; set; }
        public string artist { get; set; }
        public string text { get; set; }
    }

    public class station2
    {
        public string station { get; set; }
        public int listeners { get; set; }
        public string title { get; set; }
        public string artist { get; set; }
        public string text { get; set; }
    }

    public class station3
    {
        public string station { get; set; }
        public int listeners { get; set; }
        public string title { get; set; }
        public string artist { get; set; }
        public string text { get; set; }
    }

    public class RadioRootObject
    {
        public station1 station1 { get; set; }
        public station2 station2 { get; set; }
        public station3 station3 { get; set; }
    }

root

和

songHistory

保持为null，因此引发NullReferenceException

station1

和

station2

用于

Button2\u-Tap

和

Button3\u-Tap

，未在上述代码中显示，与上述

Button1\u-Tap

类似

我被告知DataContractJsonSerializer无法将json对象中的属性“1”与RadioRootObject类上的属性station1匹配，但我不确定如何使其匹配

---

我无法更改JSON本身中的数据。有什么想法吗？

因为JSON中的属性是“1”，而RadioRootObject成员的名称是“station1”，所以它们不匹配。您可以使用DataMemberAttribute告诉序列化程序JSON中的名称，如

public class RadioRootObject
{
    [DataMember(Name="1")]
    public station1 station1 { get; set; }
    [DataMember(Name="2")]
    public station2 station2 { get; set; }
    [DataMember(Name="3")]
    public station3 station3 { get; set; }
}

---

老实说，我认为您的类和成员必须具有[DataContract]和[DataMember]属性（请参阅），但我可能错了：-）

因为JSON中的属性是“1”，RadioRootObject的成员的名称是“station1”，这两个属性不匹配。您可以使用DataMemberAttribute告诉序列化程序JSON中的名称，如

public class RadioRootObject
{
    [DataMember(Name="1")]
    public station1 station1 { get; set; }
    [DataMember(Name="2")]
    public station2 station2 { get; set; }
    [DataMember(Name="3")]
    public station3 station3 { get; set; }
}

---

老实说，我以为你的类和成员必须有[DataContract]和[DataMember]属性（请参阅），但我可能错了：-）

查看这篇博客文章，了解如何

因此，试试这个

private void Button_Click(object sender, RoutedEventArgs e)
    {
        Button1.FontSize = 15;
        Button1.Content = "Fetching...";var client = new WebClient();
        var uri = new Uri("http://www.reignofcomputer.com/tmpsend/nowplaying.json");
        client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
        client.DownloadStringAsync(uri);
    }

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        var jobj = JObject.Parse(e.Result);
        var station3 = jobj["3"];
        Button1.Content = station3["text"];
    }

---

查看此博客文章了解如何

因此，试试这个

private void Button_Click(object sender, RoutedEventArgs e)
    {
        Button1.FontSize = 15;
        Button1.Content = "Fetching...";var client = new WebClient();
        var uri = new Uri("http://www.reignofcomputer.com/tmpsend/nowplaying.json");
        client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
        client.DownloadStringAsync(uri);
    }

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        var jobj = JObject.Parse(e.Result);
        var station3 = jobj["3"];
        Button1.Content = station3["text"];
    }

---

太棒了，成功了。非常感谢。太棒了，成功了。非常感谢。