NullReferenceException when adding migration

[clement911]

EF Core version: 8.0.3 Database provider: Microsoft.EntityFrameworkCore.SqlServer 8.0.3 Target framework: .NET 8.0 Operating system: Windows 11 x64 IDE: VS 2002 17.8

We are getting a NullReferenceException when trying to add a new migration.

Build started...
Build succeeded.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Metadata.Internal.ColumnBase`1.Microsoft.EntityFrameworkCore.Metadata.IColumnBase.get_ProviderValueComparer()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Diff(IColumn source, IColumn 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.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(IRelationalModel source, IRelationalModel 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, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
   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.

Repro: https://github.com/clement911/EfNullMigration

[clement911]

@maumar have you had any luck reproducing this issue?

[maumar]

I didn't get a chance to look into it yet. We have a huge backlog of work items at the moment, so response times are longer than usual. I will post my findings as soon as I get to it. Apologies for the delays!

[clement911]

I understand. Thanks for the update and I look forward to seeing your findings.

[clement911]

It would be good if you could at least confirm that this is a bug that will be fixed?

[JelleHissink]

I have the same issue. It involves adding a migration for DateOnly. The IsNullable of the stored previous schema incorrectly returns true. The new model returns false. I am still investigating why this previous migration indicates that the column was nullable when this property is unchanged.

[clement911]

I also suspected it was related to DateOnly

[JelleHissink]

I tried reproducing my problem in a small new solution howerver I was unable. But after some more investigation about a warning about <DateOnly?> not being valid, I found my issue. It all boils down to having a class named DateOnly in my solution, and thus the DateOnly type referenced in the model that is built not a value type but my custom reference type. Thus nullable and not having any valueconverters.

In my case this class was created by adding a migration named "DateOnly" a while ago.

dotnet ef migrations add DateOnly

I renamed my class and my issue seems resolved.

[clement911]

Thank you @JelleHissink , I can confirm that this was the same root cause for us and that renaming the migration class fixes the issue. @maumar are there any unintended consequences to renaming a migration class?

[JelleHissink]

No, I don't see an issue in renaming, according to me it acts only on the attributes, just also make sure you rename the classname in the .Designer.cs too.