Question

我在最近转换为dotnet core 2.1的项目中得到NullReferenceException。

我的EF库项目是dotnet core 2.1。代码优先迁移。

CsvHelper 6.0.2
Microsoft.EntityFrameworkCore 2.1.0
Microsoft.EntityFrameworkCore.Design 2.1.0
Microsoft.EntityFrameworkCore.SqlServer 2.1.0
Microsoft.EntityFrameworkCore.Tools 2.1.0

add-migration命令的输出

PM> add-migration -Name MyMigration -Context EscData01Context -Project Data\EscData01 -StartupProject PacmsTri -verbose
Using project 'Data\EscData01'.
Using startup project 'PacmsTri'.
Build started...
Build succeeded.
C:\Program Files\dotnet\dotnet.exe exec --depsfile C:\temp\PacmsTri\dev\***\source\PacmsTri\bin\Debug\netcoreapp2.1\PacmsTri.deps.json --additionalprobingpath "C:\Users\***\.nuget\packages" --additionalprobingpath "C:\Program Files\dotnet\sdk\NuGetFallbackFolder" --runtimeconfig C:\temp\PacmsTri\dev\***\source\PacmsTri\bin\Debug\netcoreapp2.1\PacmsTri.runtimeconfig.json "C:\Users\***\.nuget\packages\microsoft.entityframeworkcore.tools\2.1.0\tools\netcoreapp2.0\any\ef.dll" migrations add MyMigration --json --context EscData01Context --verbose --no-color --prefix-output --assembly C:\temp\PacmsTri\dev\****\source\PacmsTri\bin\Debug\netcoreapp2.1\EscData01.dll --startup-assembly C:\temp\PacmsTri\dev\****\source\PacmsTri\bin\Debug\netcoreapp2.1\PacmsTri.dll --project-dir C:\temp\PacmsTri\dev\****\source\Data\EscData01\ --language C# --working-dir C:\temp\PacmsTri\dev\****\source --root-namespace Sms.Office.Data.EscData01
Using assembly 'EscData01'.
Using startup assembly 'PacmsTri'.
Using application base 'C:\temp\PacmsTri\dev\***\source\PacmsTri\bin\Debug\netcoreapp2.1'.
Using working directory 'C:\temp\PacmsTri\dev\***\source\PacmsTri'.
Using root namespace 'Sms.Office.Data.EscData01'.
Using project directory 'C:\temp\PacmsTri\dev\***\source\Data\EscData01\'.
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider...
Finding IWebHost accessor...
Using environment 'Development'.
Using application service provider from IWebHost accessor on 'Program'.
Found DbContext 'AuthDbContext'.
Found DbContext 'DmsContext'.
Found DbContext 'EscData01Context'.
Found DbContext 'MailServicesContext'.
Found DbContext 'PmsDdContext'.
Finding DbContext classes in the project...
Using context 'EscData01Context'.
Microsoft.EntityFrameworkCore.Infrastructure[10403]
      Entity Framework Core 2.1.0-rtm-30799 initialized 'EscData01Context' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
Finding design-time services for provider 'Microsoft.EntityFrameworkCore.SqlServer'...
Using design-time services from provider 'Microsoft.EntityFrameworkCore.SqlServer'.
Finding design-time services referenced by assembly 'PacmsTri'.
No referenced design-time services were found.
Finding IDesignTimeServices implementations in assembly 'PacmsTri'...
No design-time services were found.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Metadata.Internal.TableMapping.<>c.<GetRootType>b__10_0(IEntityType t)
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.TableMapping.GetRootType()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetSortedProperties(TableMapping target)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Add(TableMapping target, DiffContext diffContext)+MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.DiffCollection[T](IEnumerable`1 sources, IEnumerable`1 targets, DiffContext diffContext, Func`4 diff, Func`3 add, Func`3 remove, Func`4[] predicates)+MoveNext()
   at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Sort(IEnumerable`1 operations, DiffContext diffContext)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetDifferences(IModel source, IModel target)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Object reference not set to an instance of an object.
PM>

我尝试将IDesignTimeServices对象添加到我的启动项目中，并尝试添加一个IDesignTimeDbContextFactory。我还尝试使用相同的dotnet和EF版本号创建一个新的示例项目，指向相同的数据库，并且能够生成上下文并成功创建迁移。因此，我看不到的两个项目之间一定有一些区别。

PM> add-migration MyMigration2 -Project ClassLibrary1 -StartupProject WebApplication20 -Context ESC_DATA01Context
Microsoft.EntityFrameworkCore.Infrastructure[10403]
      Entity Framework Core 2.1.0-rtm-30799 initialized 'ESC_DATA01Context' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
To undo this action, use Remove-Migration.

任何帮助都将不胜感激。

更新：

我最初发布的消息是此错误是由项目向标准2.0的迁移引起的，但是在将其转换回dotnetcore2.1之后却对此想法不屑一顾，并且错误仍然存在。

Answer 1

该错误看起来是由于对我的ModelSnapshot类中的模型的某些引用导致的，这些引用不再存在。包括我从上下文中删除AspNetCore.Identity后遗留下来的一些身份模型。

从我的EscData01ContextModelSnapshot中删除以下代码即可解决此问题。

modelBuilder.Entity("Sms.Office.Data.EscData01.Models.ExcelTemplate", b =>
{
    b.HasOne("Sms.Office.Data.EscData01.Models.File", "File")
        .WithMany()
        .HasForeignKey("FileId")
        .OnDelete(DeleteBehavior.Cascade);
});
modelBuilder.Entity("Microsoft.AspNetCore.Identity.IdentityRoleClaim<string>", b =>
{
    b.HasOne("Sms.Office.Data.EscData01.Authentication.ApplicationRole")
        .WithMany()
        .HasForeignKey("RoleId")
        .OnDelete(DeleteBehavior.Cascade);
});
modelBuilder.Entity("Microsoft.AspNetCore.Identity.IdentityUserClaim<string>", b =>
{
     b.HasOne("Sms.Office.Data.EscData01.Authentication.ApplicationUser")
         .WithMany()
         .HasForeignKey("UserId")
         .OnDelete(DeleteBehavior.Cascade);
});
modelBuilder.Entity("Microsoft.AspNetCore.Identity.IdentityUserLogin<string>", b =>
{
     b.HasOne("Sms.Office.Data.EscData01.Authentication.ApplicationUser")
         .WithMany()
         .HasForeignKey("UserId")
         .OnDelete(DeleteBehavior.Cascade);
});
modelBuilder.Entity("Microsoft.AspNetCore.Identity.IdentityUserRole<string>", b =>
{
     b.HasOne("Sms.Office.Data.EscData01.Authentication.ApplicationRole")
         .WithMany()
         .HasForeignKey("RoleId")
         .OnDelete(DeleteBehavior.Cascade);
     b.HasOne("Sms.Office.Data.EscData01.Authentication.ApplicationUser")
         .WithMany()
         .HasForeignKey("UserId")
         .OnDelete(DeleteBehavior.Cascade);
});   
modelBuilder.Entity("Microsoft.AspNetCore.Identity.IdentityUserToken<string>", b =>
{
     b.HasOne("Sms.Office.Data.EscData01.Authentication.ApplicationUser")
         .WithMany()
         .HasForeignKey("UserId")
         .OnDelete(DeleteBehavior.Cascade);
});

EF Core 2.1项目添加迁移NullReferenceException

1 个答案: