尝试获取与 webapi 2 中的实体相关的实体时出错

Question

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public class Dog
    {
        [Key, DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

        [Required]
        public string Name { get; set; }

        public DateTime? Birthdate { get; set; }

        public string Color { get; set; }

        public string Race { get; set; }

        public string ChipNumber { get; set; }

        public byte[] Photo { get; set; }



        public virtual ICollection<Record> Records { get; set; }

        public virtual User User { get; set; }

    }

public class Record
    {
        public Record()
        {
            Quota = 1;
        }

        [Key, DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

        public DateTime? Time { get; set; }

        [Required]
        public string Name { get; set; }

        public string Supplier { get; set; }

        public double? Price { get; set; }

        public int Quota { get; set; }

        public string Note { get; set; }



        public virtual Dog Dog { get; set; }

        public virtual User User { get; set; }
    }

WebapiConfig.cs：

var json = config.Formatters.JsonFormatter;
            json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
            config.Formatters.Remove(config.Formatters.XmlFormatter);

在 webapi 中调用“api/dogs”会引发异常：

{"$id":"1","Message":"发生错误。","ExceptionMessage":"The 'ObjectContent1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.","ExceptionType":"System.InvalidOperationException","StackTrace":null,"InnerException":{"$id":"2","Message":"An error has occurred.","ExceptionMessage":"Error getting value from 'Records' on 'System.Data.Entity.DynamicProxies.Dog_2EE5CBDAE5320B6E973C971E716C24610E64BF4CECE05B6719C5876F271BA911'.","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 Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value)\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 ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n at System.Web.Http.WebHost.HttpControllerHandler.<WriteBufferedResponseContentAsync>d__1b.MoveNext()","InnerException":{"$id":"3","Message":"An error has occurred.","ExceptionMessage":"An error occurred while executing the command definition. See the inner exception for details.","ExceptionType":"System.Data.Entity.Core.EntityCommandExecutionException","StackTrace":" at System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)\r\n at System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context, ObjectParameterCollection parameterValues)\r\n at System.Data.Entity.Core.Objects.ObjectQuery1.c__DisplayClass7.b__6()\r\n 在 System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n at System.Data.Entity.Core.Objects.ObjectQuery1.c__DisplayClass7.b__5()\r\n 在 System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func1 operation)\r\n at System.Data.Entity.Core.Objects.ObjectQuery1.GetResults(Nullable1 forMergeOption)\r\n at System.Data.Entity.Core.Objects.ObjectQuery1.Execute(MergeOption 合并选项）\r\n 在 System.Data.Entity.Core.Objects.DataClasses.EntityCollection1.Load(List1 集合，MergeOption mergeOption)\r\n at System.Data.Entity.Core.Objects.DataClasses.EntityCollection1.Load(MergeOption mergeOption)\r\n at System.Data.Entity.Core.Objects.DataClasses.RelatedEnd.Load()\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 代理，TItem 项）\r\n 在 System.Data.Entity.DynamicProxies.Dog_2EE5CBDAE5320B6E973C971E716C24610E64BF4CECE05B6719C5876F271BA911.get_Records()\r\n 在 GetRecords(对象)\r\n 在 Newtonsoft.Json.Serialization.DynamicValueProvider.GetValue(Object target)","InnerException":{"$id":"4","Message":"出现错误 发生。","ExceptionMessage":"已经有一个打开的 DataReader 与必须关闭的此命令相关联 首先。","ExceptionType":"System.InvalidOperationException","StackTrace":" 在 System.Data.SqlClient.SqlInternalConnectionTds.ValidateConnectionForExecute（SqlCommand 命令）\r\n 在 System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute（字符串 方法，SqlCommand 命令）\r\n 在 System.Data.SqlClient.SqlCommand.ValidateCommand（字符串方法， 布尔异步）\r\n 在 System.Data.SqlClient.SqlCommand.RunExecuteReader（CommandBehavior cmdBehavior、RunBehavior、runBehavior、布尔返回流、字符串 方法，TaskCompletionSource1 completion, Int32 timeout, Task& task, Boolean asyncWrite)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)\r\n at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)\r\n at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)\r\n at System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior)\r\n at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.<Reader>b__c(DbCommand t, DbCommandInterceptionContext1 c)\r\n at System.Data.Entity.Infrastructure.Interception.InternalDispatcher1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func3 操作，TInterceptionContext 拦截上下文， Action3 executing, Action3 已执行)\r\n at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.Reader（DbCommand 命令，DbCommandInterceptionContext 拦截上下文）\r\n 在 System.Data.Entity.Internal.InterceptableDbCommand.ExecuteDbDataReader（CommandBehavior 行为）\r\n 在 System.Data.Common.DbCommand.ExecuteReader（CommandBehavior 行为）\r\n 在 System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteStoreCommands（EntityCommand entityCommand, CommandBehavior 行为)"}}}}

Answer 1

解决了。

创建 DOG 的 DTO 并在 DOGDTO 中返回 USER 和 RECORDS 现在返回 UserId 和 RecordIds 列表