Question

我创建了一个webAPI控制器方法，它看起来如下：

 [HttpGet]
 public HttpResponseMessage RealEstates()
 {
     using (BoligsideDbContext context = new BoligsideDbContext())
     {
         List<RealEstateVm> realEstateVms = context.RealEstates.OrderByDescending(x => x.Id).ToList().Select(x => new RealEstateVm(x)).ToList();

          return Request.CreateResponse(HttpStatusCode.OK, realEstateVms);
     }
}

我的虚拟机看起来如下：

public class RealEstateVm
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Description { get; set; }
        public int Area { get; set; }
        public int Rooms { get; set; }
        public int Rent { get; set; }
        public string Picture { get; set; }
        public RealEstateType Type { get; set; } //this is just an enum
        public string Address { get; set; }
        public List<string> Images { get; set; }
        public string Name { get; set; }
        public string Email { get; set; }
        public string Phone { get; set; }
        public string Phone2 { get; set; }
        public string OriginalUrl { get; set; }
        public string OriginalSource { get; set; }
        public string City { get; set; }
        public int ZipCode { get; set; }
        public string StreetAddress { get; set; }
        public double Longtitude { get; set; }
        public double Latitude { get; set; }
}

但是每当我去端点时，我都会收到以下错误：

输入＆＃39; Boligside.ViewModels.RealEstateVm＆＃39;无法序列化。考虑使用DataContractAttribute属性标记它，并且标记您想要序列化的所有成员 DataMemberAttribute属性。如果类型是集合，请考虑使用CollectionDataContractAttribute标记它。见微软其他受支持类型的.NET Framework文档。

可能是什么问题？我不知道为什么我要用[DataContractAttribute]标记我的VM？

顺便说一下，完整的错误信息在这里：

此XML文件似乎没有任何关联的样式信息用它。文档树如下所示。一个错误已经发生了。＆＃39; ObjectContent`1＆＃39;类型无法序列化内容类型的响应正文＆＃39;应用/ XML;字符集= UTF-8＆＃39 ;. System.InvalidOperationException 错误有发生了。类型＆＃39; Boligside.ViewModels.RealEstateVm＆＃39;无法序列化。考虑使用DataContractAttribute属性标记它，并标记所有要使用DataMemberAttribute序列化的成员数属性。如果类型是集合，请考虑使用 CollectionDataContractAttribute。请参阅Microsoft .NET Framework 其他支持类型的文档。 System.Runtime.Serialization.InvalidDataContractException 在 System.Runtime.Serialization.DataContract.DataContractCriticalHelper.ThrowInvalidDataContractException（字符串消息，类型类型）at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.CreateDataContract（的Int32 id，RuntimeTypeHandle typeHandle，Type type）at System.Runtime.Serialization.DataContract.DataContractCriticalHelper.GetDataContractSkipValidation（的Int32 id，RuntimeTypeHandle typeHandle，Type type）at System.Runtime.Serialization.XmlObjectSerializerContext.GetDataContract（的Int32 id，RuntimeTypeHandle typeHandle）at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize（XmlWriterDelegator xmlWriter，Object obj，Boolean isDeclaredType，Boolean writeXsiType， Int32 declaredTypeID，RuntimeTypeHandle declaredTypeHandle）at WriteArrayOfRealEstateVmToXml（XmlWriterDelegator，Object， XmlObjectSerializerWriteContext，CollectionDataContract）at System.Runtime.Serialization.CollectionDataContract.WriteXmlValue（XmlWriterDelegator xmlWriter，Object obj，XmlObjectSerializerWriteContext context）at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue（DataContract dataContract，XmlWriterDelegator xmlWriter，Object obj， RuntimeTypeHandle declaredTypeHandle）at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType（DataContract dataContract，XmlWriterDelegator xmlWriter，Object obj， RuntimeTypeHandle declaredTypeHandle）at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent（XmlWriterDelegator writer，Object graph，DataContractResolver dataContractResolver）at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject（XmlWriterDelegator writer，Object graph，DataContractResolver dataContractResolver）at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions（XmlWriterDelegator writer，Object graph，DataContractResolver dataContractResolver）at System.Runtime.Serialization.DataContractSerializer.WriteObject（XmlWriter的作家，对象图） System.Net.Http.Formatting.XmlMediaTypeFormatter.WriteToStream（类型 type，Object value，Stream writeStream，HttpContent content）at System.Net.Http.Formatting.XmlMediaTypeFormatter.WriteToStreamAsync（类型 type，Object value，Stream writeStream，HttpContent内容， TransportContext transportContext，CancellationToken cancellationToken）---从前一个位置到底的堆栈跟踪结束抛出异常---在 System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任务任务） System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务） System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext（）

Answer 1

正如错误所说，它无法序列化并考虑添加数据契约属性..

using System.Runtime.Serialization;
[DataContract]
public class RealEstateVm
    {
        [DataMember]
        public int Id { get; set; }
        [DataMember]
        public string Title { get; set; }
        [DataMember]
        public string Description { get; set; }
        [DataMember]
        public int Area { get; set; }
        [DataMember]
        public int Rooms { get; set; }
        [DataMember]
        public int Rent { get; set; }
        [DataMember]
        public string Picture { get; set; }
        [DataMember]
        public RealEstateType Type { get; set; } //this is just an enum
        public string Address { get; set; }
        [DataMember]
        public List<string> Images { get; set; }
        public string Name { get; set; }
        [DataMember]
        public string Email { get; set; }
        [DataMember]
        public string Phone { get; set; }
        [DataMember]
        public string Phone2 { get; set; }
        [DataMember]
        public string OriginalUrl { get; set; }
        [DataMember]
        public string OriginalSource { get; set; }
        [DataMember]
        public string City { get; set; }
        [DataMember]
        public int ZipCode { get; set; }
        [DataMember]
        public string StreetAddress { get; set; }
        [DataMember]
        public double Longtitude { get; set; }
        [DataMember]
        public double Latitude { get; set; }
}

有关Data Contracts

的更多信息

Answer 2

您的DTO类缺少无参数构造函数。见这里：Why XML-Serializable class need a parameterless constructor （很抱歉醒来这个问题，但我现在遇到同样的问题）

Answer 3

从浏览器调用API不会将Accept Header设置为application / json，因此api将使用默认使用DataContractSerializer的XmlFormatter，即选择加入。

您可以像这样更改XML的默认行为

// XML Serializer Settings
var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter;
// use UseXmlSerializer because we use opu-out in out model classes
xml.UseXmlSerializer = true;

Web API - 返回复杂对象列表时出错

3 个答案: