在可为空的导航属性上尝试 $expand 时出错

Question

我正在使用最新的 ASP.NET 每晚构建。在我的 REST API（基于 EntitySetController）上，当我尝试 $expand 数据库中为空的导航属性时，我收到以下错误：

"message": "The EDM instance of type '[Communicator.Model.ContentTemplateGroup Nullable=True]' is missing the property 'GUID'.",
"type": "System.InvalidOperationException",
"stacktrace": "   at System.Web.Http.OData.EntityInstanceContext.GetPropertyValue(String propertyName)

我的休息电话是：

/ContentTemplate?$expand=ContentTemplateGroup

仅当数据库中存在不存在“ContentTemplateGroup”的“ContentTemplate”实例（空 FK）时才会发生这种情况。对于具有 ContentTemplateGroup 的 ContentTemplates，$expand 可以正常工作。我的实体如下所示：

public class ContentTemplate: IIdentifier
{
    public int? Id { get; set; }

    [Required]
    public Guid GUID { get; set; }

    public virtual ContentTemplateGroup ContentTemplateGroup { get; set; }
    public virtual ICollection<ContentTemplateField> ContentTemplateFields { get; set; }
}

public class ContentTemplateGroup : IIdentifier
{
    public int? Id { get; set; }

    [Required]
    public Guid GUID { get; set; }

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

    public virtual IList<ContentTemplate> ContentTemplate { get; set; }
}

当我尝试使用集合扩展导航属性时，我没有收到此错误。以下工作就像一个魅力：

http://localhost:64316/rest/ContentTemplate?$expand=ContentTemplateFields

更新：在使实体主键可以为空（int？）之前，对于相同的问题上下文，我遇到了不同的错误。错误是：

"message": "The cast to value type 'System.Int32' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.",
"type": "System.InvalidOperationException",
"stacktrace": "   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper.ErrorHandlingValueReader`1.GetValue(DbDataReader reader, Int32 ordinal)\r\n   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper.GetColumnValueWithErrorHandling[TColumn](Int32 ordinal)\r\n   at lambda_method(Closure , Shaper )\r\n   at System.Data.Entity.Core.Common.Internal.Materialization.Coordinator`1.ReadNextElement(Shaper shaper)\r\n   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper`1.SimpleEnumerator.MoveNext()\r\n   at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()\r\n   at System.Web.Http.OData.Formatter.Serialization.ODataFeedSerializer.WriteFeed(IEnumerable enumerable, ODataWriter writer, ODataSerializerContext writeContext)

Answer 1

这是一个已知问题 (1043: $expand fails when the navigation property being expanded is null)。我刚刚签入了fix。您能否在明天获取我们最新的夜间版本并确认问题是否已解决？