Question

（帖子底部的完整错误消息）

我知道其他几篇文章已经讨论过这个问题，但是这些帖子中提供的修补程序对我来说似乎不起作用。

我在下面提供我的所有代码。反序列化在方法parseSpellData()中。

示例JSON：

{
"_id": "58c9eb75c9e7ce9f7214efaa",
"index": 1,
"name": "Acid Arrow",
"desc": [
    "A shimmering green arrow streaks toward a target within range and bursts in a spray of acid. Make a ranged spell attack against the target. On a hit, the target takes 4d4 acid damage immediately and 2d4 acid damage at the end of its next turn. On a miss, the arrow splashes the target with acid for half as much of the initial damage and no damage at the end of its next turn."
],
"higher_level": [
    "When you cast this spell using a spell slot of 3rd level or higher, the damage (both initial and later) increases by 1d4 for each slot level above 2nd."
],
"page": "phb 259",
"range": "90 feet",
"components": [
    "V",
    "S",
    "M"
],
"material": "Powdered rhubarb leaf and an adder’s stomach.",
"ritual": "no",
"duration": "Instantaneous",
"concentration": "no",
"casting_time": "1 action",
"level": 2,
"school": {
    "url": "http://dnd5eapi.co/api/magic-schools/5",
    "name": "Evocation"
},
"classes": [
    {
        "name": "Wizard",
        "url": "http://dnd5eapi.co/api/classes/12"
    }
],
"subclasses": [
    {
        "url": "http://dnd5eapi.co/api/subclasses/2",
        "name": "Lore"
    },
    {
        "url": "http://dnd5eapi.co/api/subclasses/4",
        "name": "Land"
    }
],
"url": "http://dnd5eapi.co/api/spells/1"
}

代码：

class MainPageViewModel
{
    public ObservableCollection<Spell> availableSpells { get; set; } = new ObservableCollection<Spell>();


    public MainPageViewModel()
    {
        availableSpells = parseSpellData(getSpells());
    }


    public string getSpells()
    {
        string spells = string.Empty;

        try
        {
            HttpWebRequest request = WebRequest.Create("http://dnd5eapi.co/api/Spells") as HttpWebRequest;

            using (var response = request.GetResponse())
            {
                using (var reader = new StreamReader(response.GetResponseStream()))
                {
                    spells = reader.ReadToEnd();
                }
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
        Console.WriteLine(spells);
        return spells;
    }

    public ObservableCollection<Spell> parseSpellData(string listOfSpells)
    {
        ObservableCollection<Spell> parsedSpellData = JsonConvert.DeserializeObject<ObservableCollection<Spell>>(listOfSpells); 

        return parsedSpellData as ObservableCollection<Spell>;
    }        
}

public class School
{
    public string url { get; set; }
    public string name { get; set; }
}

public class Class
{
    public string name { get; set; }
    public string url { get; set; }
}

public class Subclass
{
    public string url { get; set; }
    public string name { get; set; }
}

public class Spell
{
    public string _id { get; set; }
    public int index { get; set; }
    public string name { get; set; }
    public List<string> desc { get; set; }
    public List<string> higher_level { get; set; }
    public string page { get; set; }
    public string range { get; set; }
    public List<string> components { get; set; }
    public string material { get; set; }
    public string ritual { get; set; }
    public string duration { get; set; }
    public string concentration { get; set; }
    public string casting_time { get; set; }
    public int level { get; set; }
    public School school { get; set; }
    public List<Class> classes { get; set; }
    public List<Subclass> subclasses { get; set; }
    public string url { get; set; }
}

PM Vizualization错误

无法将当前JSON对象（例如{“name”：“value”}）反序列化为类型'System.Collections.ObjectModel.ObservableCollection'1 [NInterpret.interpretedObject]'，因为该类型需要JSON数组（例如[1] ，2,3]）正确反序列化。要修复此错误，请将JSON更改为JSON数组（例如[1,2,3]）或更改反序列化类型，使其成为普通的.NET类型（例如，不是像整数这样的基本类型，而不是集合类型喜欢可以从JSON对象反序列化的数组或列表。

Answer 1

问题是你的JSON不是一个数组，它是一个包含数组值属性的对象。如果使用http://dnd5eapi.co/api/Spells格式化https://jsonformatter.curiousconcept.com/返回的JSON，则可以更清楚地看到这一点：

{
   "count":305,
   "results":[
      {
         "name":"Acid Arrow",
         "url":"http://www.dnd5eapi.co/api/spells/1"
      },
      {
         "name":"Acid Splash",
         "url":"http://www.dnd5eapi.co/api/spells/2"
      }
      // Additional entries omitted
   ]
}

因此，您需要反序列化为包含"results"集合的模型，而不是集合本身。一种简单的方法是使用JsonConvert.DeserializeAnonymousType()指定包装器根对象：

public ObservableCollection<Spell> parseSpellData(string listOfSpells)
{
    var parsedSpellData = JsonConvert.DeserializeAnonymousType(listOfSpells, new { results = (ObservableCollection<Spell>)null });

    return parsedSpellData.results;
}

工作fiddle #1。

当然，您也可以为根指定显式类型 - 事实上，如果您将[JsonProperty("results")]添加到MainPageViewModel，则availableSpells可用于此目的：

class MainPageViewModel
{
    [JsonProperty("results")]
    public ObservableCollection<Spell> availableSpells { get; set; } = new ObservableCollection<Spell>();

    public MainPageViewModel()
    {
        JsonConvert.PopulateObject(getSpells(), this);
    }

示例工作fiddle #2。

实际上，您的数据模型似乎有许多JSON中没有的属性，其中返回的"results"数组中返回的对象仅包含"name"和"url"属性。您确定要为此特定API使用正确的数据模型吗？

<强>更新

您的问题中发布的JSON似乎是由返回结果中列出的特定拼写API网址返回的，例如http://www.dnd5eapi.co/api/spells/1，它还对应于您的Spell类型。如果您想一次获取所有拼写数据，可以引入以下类型

public class NameAndUri
{
    public string url { get; set; }
    public string name { get; set; }
}

public class NameAndUri<T> : NameAndUri
{
    public T Deserialize()
    {
        return JsonExtensions.DeserializeFromUri<T>(url);
    }
}

public static partial class JsonExtensions
{
    public static T DeserializeAnonymousTypeFromUri<T>(string uri, T anonymousTypeObject)
    {
        return DeserializeFromUri<T>(uri);
    }

    public static T DeserializeFromUri<T>(string uri)
    {
        HttpWebRequest request = WebRequest.Create(uri) as HttpWebRequest;
        using (var response = request.GetResponse())
        using (var reader = new StreamReader(response.GetResponseStream()))
        using (var jsonReader = new JsonTextReader(reader))
        {
            return JsonSerializer.CreateDefault().Deserialize<T>(jsonReader);
        }
    }
}

按如下方式修改MainPageViewModel：

class MainPageViewModel
{
    public const string spellUri = "http://dnd5eapi.co/api/Spells";

    public ObservableCollection<Spell> availableSpells { get; set; } // = new ObservableCollection<Spell>();

    public MainPageViewModel()
    {
        availableSpells = parseSpellData(spellUri);
    }

    static ObservableCollection<Spell> parseSpellData(string spellUri)
    {
        var parsedSpellData = JsonExtensions.DeserializeAnonymousTypeFromUri(spellUri, new { results = (List<NameAndUri<Spell>>)null });            
        var query = parsedSpellData.results.Select(s => s.Deserialize());
        return new ObservableCollection<Spell>(query);
    }   
}

注意：

根据Newtonsoft: Performance Tips中的建议，我直接从响应流反序列化，而不是加载到中间string。
对于某些适当的School，您可能希望将Class，Subclass和NameAndUri<T>类型替换为T。
< / LI>
如果同时加载所有法术的表现不够好，请考虑转到async solution。

示例fiddle #3超时https://dotnetfiddle.net/但在本地工作。

无法将当前json对象反序列化为ObservableCollection

1 个答案: