Question

我正在使用最新的ASP.NET nightly版本。在我的REST API（基于EntitySetController）上，当我尝试$扩展数据库中为null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)

休息电话Im macking是：

/ContentTemplate?$expand=ContentTemplateGroup

仅当存在数据库中存在“ContentTemplateGroup”的“ContentTemplate”实例（null FK）时才会发生这种情况。对于具有ContentTemplateGroup的ContentTemplates，$ expand工作正常。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; }
}

当我尝试使用集合展开导航属性时，我没有收到此错误。以下作品很有魅力：

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

更新：在使实体主键为nullable（int？）之前，我遇到了同一问题上下文的不同错误。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）。我刚刚检查了fix。你明天可以抓住我们最新的夜间制作并确认问题是否已经消失了吗？

在可空的导航属性上尝试$ expand时出错

1 个答案: