C# Entity Framework 错误通过枚举将 nvarchar 转换为 int

Question

我收到以下错误时遇到问题：

Conversion failed when converting the nvarchar value 'HolidayRequest' to data type int.

我在实体框架中有一个继承结构。我的基本模型如下：

public abstract class Request
{
    public int ID { get; set; }
    public int EmployeeID { get; set; }
    public string Subject { get; set; }

    [Display(Name = "Date Requested")]
    public DateTime DateRequested { get; set; }
    [Display(Name = "Start Date")]
    public DateTime StartDateTime { get; set; }
    [Display(Name = "Return To Work Date")]
    public DateTime EndDateTime { get; set; }
    public RequestStatus Status { get; set; }
    public string Notes { get; set; }
    public int? ResponseID { get; set; }
    public RequestDiscriminator Discriminator { get; set; }

    [ForeignKey("EmployeeID")]
    public virtual Employee Employee { get; set; }
    [ForeignKey("ResponseID")]
    public virtual Response Response { get; set; }
}

当我尝试从数据库中检索数据时：

    public IQueryable<Request> GetPendingHolidayRequestsByEmployeeId(int employeeId)
    {
        var list = _context.Requests.Where(p => p.Discriminator == RequestDiscriminator.Holiday && p.EmployeeID == employeeId && p.Status == RequestStatus.NotProcessed);
        return list;
    }

这是发生错误的地方。

鉴于错误的上下文，我认为这是此枚举 public RequestDiscriminator Discriminator { get; set; } 的问题

枚举的结构是：

public enum RequestDiscriminator
{
    Holiday,
    Absence
}

实体框架正在发送的SQL语句是：

SELECT 
[Extent1].[ID] AS [ID], 
CASE WHEN ([Extent1].[Discriminator1] = N'AbsenceRequest') THEN '0X0X' ELSE '0X1X' END AS [C1], 
[Extent1].[EmployeeID] AS [EmployeeID], 
[Extent1].[Subject] AS [Subject], 
[Extent1].[DateRequested] AS [DateRequested], 
[Extent1].[StartDateTime] AS [StartDateTime], 
[Extent1].[EndDateTime] AS [EndDateTime], 
[Extent1].[Status] AS [Status], 
[Extent1].[Notes] AS [Notes], 
[Extent1].[ResponseID] AS [ResponseID], 
[Extent1].[Discriminator] AS [Discriminator]
CASE WHEN ([Extent1].[Discriminator1] = N'AbsenceRequest') THEN [Extent1].[ReasonCode] END AS [C2], 
CASE WHEN ([Extent1].[Discriminator1] = N'AbsenceRequest') THEN [Extent1].[TakenPaid] END AS [C3], 
CASE WHEN ([Extent1].[Discriminator1] = N'AbsenceRequest') THEN CAST(NULL AS float) ELSE [Extent1].[TotalDays] END AS [C4], 
CASE WHEN ([Extent1].[Discriminator1] = N'AbsenceRequest') THEN [Extent1].[Employee_EmployeeID] END AS [C5], 
CASE WHEN ([Extent1].[Discriminator1] = N'AbsenceRequest') THEN CAST(NULL AS int) ELSE [Extent1].[Employee_EmployeeID1] END AS [C6]
FROM [dbo].[Request] AS [Extent1]
WHERE ([Extent1].[Discriminator1] IN (N'AbsenceRequest',N'HolidayRequest')) AND (0 = [Extent1].[Discriminator]) AND (0 = [Extent1].[Status])

任何帮助将不胜感激，因为我完全被难住了。

更新

根据以下答案中的建议，我已从数据库中删除了两个鉴别器列并重新读取了我的。但是，SQL 查询似乎仍在寻找现在不存在的 Discriminator1 列。

Answer 1

我已经设法解决了这个问题。答案是删除我创建的鉴别器列，并允许 EF 通过在 linq 查询中包含类型来确定类型，如下所示：

var test = _context.Requests.Where(r => r.EmployeeID == employeeId).OfType<AbsenceRequest>();

OfType() 似乎告诉 EF 查看该类型名称的鉴别器列，并且只返回该类型的数据。

Answer 2

看起来您在“Discriminator1”中有一个额外的列。您是否最初将该字段作为字符串，然后尝试将其转换为枚举？最好的选择可能是尝试完全丢弃该字段并确保它同时丢弃 Discriminator 和 Discriminator1。然后尝试将其添加回来。这可能发生在具有自定义映射时，因此可能会出现问题。