问在WebAPI中使用实体框架对表进行GET调用时的异常

EN

我正在尝试创建一个WebApi来使用实体框架从DB读取数据。

我的数据模型设计如下：

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我添加了一个名为WebApi的SportsController控制器，如下所示：

public class SportsController : ApiController
{
    public HttpResponseMessage Get()
    {
        try
        {
            using (MyLeagueDBEntities dbEntity = new MyLeagueDBEntities())
            {
                return Request.CreateResponse(HttpStatusCode.OK, dbEntity.tbl_Sports.ToList());
            }
        }
        catch (Exception ex)
        {
            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
        }
    }
}

在从浏览器调用请求到我的WebApi控制器GET方法时，我将得到如下所示的异常。但是在调试模式下，我可以看到它能够从数据库中获得数据，不会出现任何错误，但是一旦控件移出该方法，它就会抛出下面的异常。

例外细节：

“消息”：“发生了错误”， “'ObjectContent1' 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":"Error getting value from 'tbl\_Tournament' on 'System.Data.Entity.DynamicProxies.tbl\_Sports\_7461105FEAC4FCCBDED534FCE44707AF9C7DFE1E4AD69B1E7E3777FBB953F184'.", "ExceptionType":"Newtonsoft.Json.JsonSerializationException", "StackTrace":" at Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CalculatePropertyValues(JsonWriter writer, Object value, JsonContainerContract contract, JsonProperty member, JsonProperty property, JsonContract& memberContract, Object& memberValue)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n > at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n at System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n End of stack trace from previous location where exception was thrown at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.WebHost.HttpControllerHandler.d\_\_1b.MoveNext()", "InnerException":{"Message":"An error has occurred.", "ExceptionMessage":"The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.", "ExceptionType":"System.ObjectDisposedException", "StackTrace":" at System.Data.Entity.Core.Objects.ObjectContext.get\_Connection()\r\n at System.Data.Entity.Core.Objects.ObjectQuery1.GetResults(Nullable1 forMergeOption)\r\n at System.Data.Entity.Core.Objects.ObjectQuery1.Execute(MergeOption System.Data.Entity.Core.Objects.DataClasses.EntityCollection1.Load(List1”：“System.Data.Entity.Core.Objects.DataClasses.EntityCollection1.Load(MergeOption mergeOption)\r\n at System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.DeferredLoad()\r\n at System.Data.Entity.Core.Objects.Internal.LazyLoadBehavior.LoadProperty[TItem](TItem propertyValue, String relationshipName, String targetRoleName, Boolean mustBeNull, Object wrapperObject)\r\n at System.Data.Entity.Core.Objects.Internal.LazyLoadBehavior.<>c\_\_DisplayClass72.b__1(TProxy mergeOption)\r\nat System.Data.Entity.Core.Objects.DataClasses.EntityCollection1.Load(List1集合，MergeOption mergeOption)\r\nat System.Data.Entity.Core.Objects.DataClasses.EntityCollection1.Load(MergeOption mergeOption)\r\n at System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.DeferredLoad()\r\n at System.Data.Entity.Core.Objects.Internal.LazyLoadBehavior.LoadProperty[TItem](TItem propertyValue, String relationshipName, String targetRoleName, Boolean mustBeNull, Object wrapperObject)\r\n at System.Data.Entity.Core.Objects.Internal.LazyLoadBehavior.<>c\_\_DisplayClass72.b__1(TProxy proxy，TItem item)\r\n 在System.Data.Entity.DynamicProxies.tbl_Sports_7461105FEAC4FCCBDED534FCE44707AF9C7DFE1E4AD69B1E7E3777FBB953F184.get_tbl_Tournament()\r\n 在Gettbl_Tournament(Object )\r\n 在Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object目标)“}

我是实体框架( Entity )和WebApi的新手，请求实体框架帮助我解决这个问题。

PFB带有错误消息的快照登录在fiddler上。当前收到Http 500内部服务器错误，

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