C# asp.net web api中的即时加载

大家好，我最近开始学习如何编写web api

我在winform中有一个项目，我想使用web api重新制作，问题是我不能使用即时加载，我总是得到错误500，代码如下：

public HttpResponseMessage GetExpediente()
    {
        db.Configuration.ProxyCreationEnabled = false;
        var expediente = db.Expediente.Include(x=>x.Documento);
        if (expediente.Any())
        {
            return Request.CreateResponse(HttpStatusCode.OK, expediente);
        }
        else
        {
            return Request.CreateErrorResponse(HttpStatusCode.NotFound,
                "No se encontraron expedientes.");
        }
    }

public class A
{
    public B B { get; set; }
}

public class B
{
    public virtual ICollection<A> A { get; set; }
}

我经常遇到的错误是：

{"Message":"An error has occurred.","ExceptionMessage":"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.","ExceptionType":"System.InvalidOperationException","StackTrace":null,"InnerException":{"Message":"An error has occurred.","ExceptionMessage":"Self referencing loop detected for property 'Expediente' with type 'Modelo.Expediente'. Path '[0].Documento[0]'.","ExceptionType":"Newtonsoft.Json.JsonSerializationException","StackTrace":"   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CheckForCircularReference(JsonWriter writer, Object value, JsonProperty property, JsonContract contract, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CalculatePropertyValues(JsonWriter writer, Object value, JsonContainerContract contract, JsonProperty member, JsonProperty property, JsonContract& memberContract, Object& memberValue)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n   en Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n   en System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n   en System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n   en System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content)\r\n   en System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n--- Fin del seguimiento de la pila de la ubicación anterior donde se produjo la excepción ---\r\n   en System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   en System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   en System.Web.Http.WebHost.HttpControllerHandler.<WriteBufferedResponseContentAsync>d__1b.MoveNext()"}}

{“Message”：“发生了错误”，“ExceptionMessage”：“ObjectContent`1”类型未能序列化内容类型“application/json；charset=utf-8”的响应正文”，“ExceptionType”：“System.invalidoctionexception”，“StackTrace”：null，“InnerException”：{“Message”：“发生了错误”，“ExceptionMessage”：”：“检测到类型为'Modelo.phamplite'。路径'[0].Documento[0]'，“ExceptionType:“Newtonsoft.Json.JsonSerializationException”，“StackTrace:“en Newtonsoft.Json.Serialization.jsonSerializationPrinternalWriter.CheckForCircularReference”（JsonWriter编写器，对象值，JsonProperty属性，JsonContract合同，JsonContainerContract容器合同，JsonProperty容器属性）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CalculateProperty值（JsonWriter编写器，对象值，JsonContainerContract合同，JsonProperty成员，JsonProperty属性，JsonContract&memberContract，对象&memberValue）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject（JsonWriter编写器，对象值，JsonObjectContract合约，JsonProperty成员，JsonContainerContract collectionContract，JsonProperty containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.serializationValue（JsonWriter编写器，对象值，JsonContract valueContract，JsonProperty成员，JsonContainerContract containerContract，JsonProperty containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList（JsonWriter-writer，IEnumerable-values，JsonArrayContract-contract，JsonProperty成员，JsonContainerContract-collectionContract，JsonProperty-containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter编写器，对象值，JsonContract valueContract，JsonProperty成员，JsonContainerContract containerContract，JsonProperty containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject（JsonWriter编写器，对象值，JsonObjectContract合约，JsonProperty成员，JsonContainerContract collectionContract，JsonProperty containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.serializationValue（JsonWriter编写器，对象值，JsonContract valueContract，JsonProperty成员，JsonContainerContract containerContract，JsonProperty containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList（JsonWriter-writer，IEnumerable-values，JsonArrayContract-contract，JsonProperty成员，JsonContainerContract-collectionContract，JsonProperty-containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter编写器，对象值，JsonContract valueContract，JsonProperty成员，JsonContainerContract containerContract，JsonProperty containerProperty）\r\n en Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize（JsonWriter JsonWriter，对象值，类型objectType）\r\n en Newtonsoft.Json.JsonSerializer.Serializer\n（JsonWriter JsonWriter，对象值，类型objectType）\r\n en System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream（类型类型，对象值，流writeStream，编码有效编码）\r\n en System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream（类型，对象值，流writeStream writeStream，编码有效编码）\r\n en System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream（类型、对象值、流writeStream、HttpContent内容）\r\n en System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync（类型类型、对象值、流写入流、HttpContent内容、TransportContext TransportContext、CancellationToken CancellationToken）\r\n---在系统运行时、编译器服务、TaskWaiter.ThrowForNonSuccess（任务任务任务）之前，为ubicación的用户提供服务\r\n en System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务）\r\n en System.Web.Http.WebHost.HttpControllerHandler.d_u1b.MoveNext（）“}

我一直在寻找信息。这可能会帮助我，但我总是发现我应该禁用懒散加载，我做到了，但它没有起作用，这里有人能帮我吗

顺便说一句，我的目标是从windows窗体项目中使用此api，有人告诉我这样做：

var emp1 = response.Content.ReadAsStringAsync().Result;
        var result = JsonConvert.DeserializeObject<IEnumerable<ExpedientePOCO>>(emp1);

var emp1=response.Content.ReadAsStringAsync（）.Result；
var result=JsonConvert.DeserializeObject（emp1）；

但是我从var emp1=…的行中得到的是一个错误500。哦，当我从上下文中获取include时，它工作得很好，但是我想使用渴望加载，希望您能提供帮助

谢谢！谢谢

我对DTO的理解是：

 public HttpResponseMessage GetExpediente()
    {
        db.Configuration.ProxyCreationEnabled = false;
        var expediente = db.Expediente.Include(x=>x.Documento);
        List<ExpedientePOCO> expPOCO = new List<ExpedientePOCO>();
        foreach (var entidad in expediente)
        {
            String fecha = String.Format("{0:dd-MM-yyy}", entidad.FechaCreacion);
            ExpedientePOCO expedientePOCO = new ExpedientePOCO()
            {
                idExpediente = entidad.idExpediente,
                NombreExpediente = entidad.NombreExpediente,
                FechaCreacion = Convert.ToDateTime(fecha),
                DuenioExpediente = entidad.DuenioExpediente,
                CantidadDocumento = entidad.CantidadDocumento
            };
            foreach (var documentos in entidad.Documento)
            {
                DocumentoPOCO documento = new DocumentoPOCO()
                {
                    idDocumento = documentos.idDocumento,
                    idExpediente = documentos.idExpediente,
                    NombreDocumento = documentos.NombreDocumento,
                    FechaCreacion = documentos.FechaCreacion,
                    Expedientes = expedientePOCO
                };
                expedientePOCO.Documentos.Add(documento);
            }
            expPOCO.Add(expedientePOCO);
        }
        if (expPOCO.Any())
        {
            return Request.CreateResponse(HttpStatusCode.OK, expPOCO);
        }
        else
        {
            return Request.CreateErrorResponse(HttpStatusCode.NotFound,
                "No se encontraron expedientes.");
        }
    }

public HttpResponseMessage getenvigate（）
{
db.Configuration.ProxyCreationEnabled=false；
var便利=数据库便利。包括（x=>x.Documento）；
List expPOCO=新列表（）；
foreach（权宜之计中的var entidad）
{
字符串fecha=String.Format（“{0:dd-MM-yyy}”，entidad.fechacreation）；
权宜TEPOCO权宜TEPOCO=新权宜TEPOCO（）
{
idexpedinte=entidad.idexpedinte，
nombreexpedinte=entidad.nombreexpedinte，
fechacreaction=转换到当前时间（fecha），
dueniophamplite=entidad.dueniophamplite，
CantidadDocumento=entidad.CantidadDocumento
};
foreach（entidad.Documento中的var documentos）
{
DocumentoPOCO documento=新DocumentoP
public class ADTO
{
    // needed properties only
    public BDTO B { get; set; }
}

public class BDTO
{
    // needed properties only
    public List<ADTO> A { get; set; }
}

var data = db.As
    .Select(a => new ADTO 
    {
        x = a.x ....
        B = new BDTO { x = a.B.x ...  }
    }
    .ToList();

var data = context.B
    .Select(b => new BDTO
    {
        x = b.x ...
        A = b.A
            .Select(a => new ADTO
            {
                x = a.x ...
            }
            .ToList()
    }
    .ToList();