Question

我有一个ASP.NET Web API GET端点

public class MyType
{
  public bool Active { get; set; }
  public DateTime CreateDate { get; set; }
  public int Id { get; set; }
  public string Description { get; set; }
}

public class MyResponse
{
  public List<MyType> Results { get; set; }
}

[HttpGet]
public MyResponse GetResults()

对于结果包含2个项目的情况，json返回字符串是

{"Results":[{"Active":true,"CreateDate":"2014-01-01T00:00:00","Id":1,"Description":"item 1 description"},{"Active":true,"CreateDate":"2014-01-01T00:00:00","Id":2,"Description":"item 2 description"}]}

在客户端，我希望将json反序列化为List<MyType>

（简洁的语言略显松散）

List<MyType> results = HttpResponseMessage.Content.ReadAsAsync<List<MyType>>(new [] { new JsonMediaTypeFormatter () }).Result;

但这会引发异常

Newtonsoft.Json.JsonSerializationException: Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[MyType]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.
To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List<T>) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.

   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)
   at System.Net.Http.Formatting.JsonMediaTypeFormatter.<>c__DisplayClass8.<ReadFromStreamAsync>b__6()
   at System.Threading.Tasks.TaskHelpers.RunSynchronously[TResult](Func`1 func, CancellationToken cancellationToken)

Answer 1

您的Web API方法返回一个对象，而不是一个列表 - 您试图强制反序列化程序将其重新构建为列表 - 这不会起作用。

您需要：

使用GetResults()方法返回列表本身（即将其从MyResponse更改为List<MyType>，或者
在客户端，将收到的数据转换为MyResponse，而不是List<MyType>。

Answer 2

MyResponse类是序列化为JSON的类，因此这是调用ReadAsAsync方法时应该使用的类型。

MyResponse responseContent = HttpResponseMessage.Content.ReadAsAsync<MyResponse>(new [] { new JsonMediaTypeFormatter () });

然后，如果您想访问结果列表，请使用responseContent.Results

从我见过的示例中，您也可以省略IEnumerable<MediaTypeFormatter>参数，因此这也可以。 http://msdn.microsoft.com/en-us/library/hh944541(v=vs.118).aspx

MyResponse responseContent = HttpResponseMessage.Content.ReadAsAsync<MyResponse>();

JSON反序列化为List <t> </t>

2 个答案: