System.NullReferenceException: Object reference not set to an instance of an object.

[ZevFung]

I need to delete a property in the class, and then execute add migration command, but the error is prompted

Steps to reproduce

model

using System.Collections.Generic;

namespace Domain
{
   public class Province
    {
        public Province()
        {
            Cities = new List<City>();
        }
        public int Id { get; set; }

        public string Name { get; set; }

        public string Code { get; set; }

        public List<City> Cities { get; set; }
    }
}

namespace Domain
{
    public class City
    {
        public int Id { get; set; }

        
        public string Name { get; set; }

        public string Code { get; set; }

        public string CodeName1 { get; set; }

        public int ProvinceId { get; set; }

        public Province Province { get; set; }
    }
}

I delete the CodeName1 attribute in the City class, and execute the command Add-Migration DelCodeName1 -verbose ,following error is returned.

PM> Add-Migration DelCodeName1 -verbose
Using project 'Data'.
Using startup project 'Data'.
Build started...
Build succeeded.
C:\Program Files\dotnet\dotnet.exe exec --depsfile C:\Users\pxm\source\repos\WebApplication8\Data\bin\Debug\netcoreapp3.1\Data.deps.json --additionalprobingpath C:\Users\pxm\.nuget\packages --additionalprobingpath "C:\Program Files\dotnet\sdk\NuGetFallbackFolder" --runtimeconfig C:\Users\pxm\source\repos\WebApplication8\Data\bin\Debug\netcoreapp3.1\Data.runtimeconfig.json C:\Users\pxm\.nuget\packages\microsoft.entityframeworkcore.tools\5.0.0-preview.2.20120.8\tools\netcoreapp2.0\any\ef.dll migrations add DelCodeName1 --json --verbose --no-color --prefix-output --assembly C:\Users\pxm\source\repos\WebApplication8\Data\bin\Debug\netcoreapp3.1\Data.dll --startup-assembly C:\Users\pxm\source\repos\WebApplication8\Data\bin\Debug\netcoreapp3.1\Data.dll --project-dir C:\Users\pxm\source\repos\WebApplication8\Data\ --language C# --working-dir C:\Users\pxm\source\repos\WebApplication8 --root-namespace Data
Using assembly 'Data'.
Using startup assembly 'Data'.
Using application base 'C:\Users\pxm\source\repos\WebApplication8\Data\bin\Debug\netcoreapp3.1'.
Using working directory 'C:\Users\pxm\source\repos\WebApplication8\Data'.
Using root namespace 'Data'.
Using project directory 'C:\Users\pxm\source\repos\WebApplication8\Data\'.
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider...
Finding Microsoft.Extensions.Hosting service provider...
No static method 'CreateHostBuilder(string[])' was found on class 'Program'.
No application service provider was found.
Finding DbContext classes in the project...
Found DbContext 'MyDBContext'.
Using context 'MyDBContext'.
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 'Data'.
No referenced design-time services were found.
Finding IDesignTimeServices implementations in assembly 'Data'...
No design-time services were found.
DetectChanges starting for 'MyDBContext'.
DetectChanges completed for 'MyDBContext'.
DetectChanges starting for 'MyDBContext'.
DetectChanges completed for 'MyDBContext'.
'MyDBContext' disposed.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Initialize(ColumnOperation columnOperation, IProperty property, CoreTypeMapping typeMapping, Boolean isNullable, IEnumerable`1 migrationsAnnotations, Boolean inline)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Add(IProperty target, DiffContext diffContext, Boolean inline)+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.Diff(ITable source, ITable 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_0.<.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.

I'm going back to version 3.1. 2.Everything is OK

Further technical details

EF Core version:5.0.0-preview.2.20120.8
Database provider: Microsoft.EntityFrameworkCore.SqlServer 5.0.0-preview.2.20120.8
Target framework: NET Core 3.1
Operating system:Windows 10
IDE: Microsoft Visual Studio Enterprise 2019 16.4.6

[ajcvickers]

@bricelam @AndriySvyryd This looks like a 5.0 regression.

[AndriySvyryd]

This is likely going to be fixed in #20305

[ajcvickers]

Note for team: I can reproduce this on preview 1 and current daily build. I will test again after #20305 is merged.

[ajcvickers]

Verified that this is fixed in the latest daily builld.

[tonyfa]

Removed and added back in the table using Scaffold-DbContext and the error went away