我從.NET5升級到.NET6，現在從LINQ查詢中獲取SqlNullValueException

我剛剛將一個專案從 .NET 5 升級到了 .NET 6 預覽版，并開始使用 Visual Studio 2022。但我得到了一個我以前沒有得到的 SqlNullValueException。這對我來說沒有意義。

這是 LINQ 查詢：

var clients = _dbContext.AppUserAppUsers
            .Where(x => x.AppUserParentId == designerId
                        && x.ChildAppUser.AppUserRole == AppUserRole.Client)
            .Include(x => x.ChildAppUser.Profile)
            .Select(x => x.ChildAppUser)
            .AsNoTracking();

return clients.ToList();

AppUserAppUsers 物體是 AppUsers 的多對多模型。我正在使用 Table-per-hierarchy 模式 所以我有 AppUserBase 抽象類，DesignerModel 和 ClientModel 都擴展了該類。

public class AppUserAppUser
    {
        public int AppUserParentId { get; set; }

        public int AppUserChildId { get; set; }

        public bool Active { get; set; }

        public AppUserBase ParentAppUser { get; set; }

        public AppUserBase ChildAppUser { get; set; }
    }

同樣，所有這些在 .NET 5 中都能完美運行！

對 ToList() 的呼叫會引發此例外：

System.Data.SqlTypes.SqlNullValueException
  HResult=0x80131931
  Message=Data is Null. This method or property cannot be called on Null values.
  Source=Microsoft.Data.SqlClient
  StackTrace:
   at Microsoft.Data.SqlClient.SqlBuffer.ThrowIfNull()
   at Microsoft.Data.SqlClient.SqlBuffer.get_String()
   at Microsoft.Data.SqlClient.SqlDataReader.GetString(Int32 i)
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Design2WorkroomApi.Repository.AppUserRepository.GetClientsByDesignerId(Int32 designerId) in C:\Users\davew\source\repos\Design2WorkroomApi\Design2WorkroomApi\Repository\AppUserRepository.cs:line 65
   at Design2ClientAPI.Controllers.ClientsController.GetClientsByDesignerId(Int32 designerId) in C:\Users\davew\source\repos\Design2WorkroomApi\Design2WorkroomApi\Controllers\ClientsController.cs:line 56
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeNextActionFilterAsync()

如果我取出 Include 和 Select 呼叫，這可以正常作業。但是任一和 LINQ 陳述句都回傳 null。

在 .NET 5 版本中，使用相同引數的相同方法可以正常作業。我以前多次使用過類似的代碼，沒有任何問題。

Obviously, something in .NET 6 has changed to cause this, but I don't know what it is.

Here are my Entity Framework Core packages. I had the same issue before I upgraded these packages.

 <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="6.0.0-rc.2.21480.10" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="6.0.0-rc.2.21480.5" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.0-rc.2.21480.5" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="6.0.0-rc.2.21480.5">

uj5u.com熱心網友回復：

洗掉.Include()，在這種特殊情況下不需要它，它可能會導致您遇到的錯誤。

新查詢應該看起來像：

var clients = _dbContext.AppUserAppUsers
            .Where(x => x.AppUserParentId == designerId
                        && x.ChildAppUser.AppUserRole == AppUserRole.Client)
            .Select(x => x.ChildAppUser)
            .AsNoTracking();

標籤：c# .net linq asp.net-core entity-framework-core

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