Question

我为数据库中的视图创建了EF Code First Entity。我设置了一个测试，访问代码在我的测试中工作，但是当我在测试之外运行代码时，它会抛出“Object Reference not set to a object of object”。我被卡住了，因为我无法理解可能导致问题的原因。关于它为什么会抛出错误的任何想法？

这是我的实体类：

using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace PhoenixData.Models.DB
{
    public partial class VW_ICD10MappingWithUsage
    {
        [Key]
        [Column(Order = 0)]
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public long Id { get; set; }

        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int ProviderID { get; set; }

        [StringLength(20)]
        public string DxKey { get; set; }

        [StringLength(100)]
        public string Icd9Description { get; set; }

        [StringLength(10)]
        public string Code { get; set; }

        [StringLength(2000)]
        public string Description { get; set; }

        public int? USAGE { get; set; }

        [Key]
        [Column(Order = 1)]
        [StringLength(20)]
        public string Region { get; set; }

        public long? ProviderCodeCount { get; set; }

        [NotMapped]
        public IList<CodeProviderUsage> ChildUsages { get; set; } 

        public VW_ICD10MappingWithUsage()
        {
        ChildUsages = new List<CodeProviderUsage>();
        }
    }
}

以下是引发错误的访问代码：

using (var dbContext = new MyDatabase(_config.ConnectionString))
{
    res = dbContext.VW_ICD10MappingWithUsage
    .Where(x => x.ProviderID == providerId)
    .OrderBy(x => x.DxKey)
    .Take(pageSize)
    .ToList();
}

这是堆栈跟踪：

   at System.Object.GetType()
   at System.Data.Entity.Core.EntityKey.ValidateTypeOfKeyValue(MetadataWorkspace workspace, EdmMember keyMember, Object keyValue, Boolean isArgumentException, String argumentName)
   at System.Data.Entity.Core.EntityKey.ValidateEntityKey(MetadataWorkspace workspace, EntitySet entitySet, Boolean isArgumentException, String argumentName)
   at System.Data.Entity.Core.Objects.ObjectStateManager.CheckKeyMatchesEntity(IEntityWrapper wrappedEntity, EntityKey entityKey, EntitySet entitySetForType, Boolean forAttach)
   at System.Data.Entity.Core.Objects.ObjectStateManager.AddEntry(IEntityWrapper wrappedObject, EntityKey passedKey, EntitySet entitySet, String argumentName, Boolean isAdded)
   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper.HandleEntityAppendOnly[TEntity](Func`2 constructEntityDelegate, EntityKey entityKey, EntitySet entitySet)
   at lambda_method(Closure , Shaper )
   at System.Data.Entity.Core.Common.Internal.Materialization.Coordinator`1.ReadNextElement(Shaper shaper)
   at System.Data.Entity.Core.Common.Internal.Materialization.Shaper`1.SimpleEnumerator.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at PhoenixData.Core.ICD10.ICD10MappingRepository.SearchIcd10MappingWithUsages(Int32 pageSize, Int32 pageNumber, Int32 providerId, String orderByColumnName, String direction, String searchTerm, String searchColumns) in C:\Dev\PhoenixDriveServices\PhoenixData\Core\ICD10\ICD10MappingRepository.cs:line 149

Answer 1

OP接受的答案是：

那么一条特定记录是否有可能在实现时导致问题？例如，您的一个列在模型中不可为空，但它在数据库中可以为空，实际值为null会混淆实现？换句话说，尝试将问题缩小到数据库中的特定行。

看起来就是这样。其中一行的复合键列之一为空。

代码优先：在测试中可访问的实体，但在测试之外“未设置为对象的实例”

1 个答案: