Efcore: Multiple properties with default implementation in an interface, applied to an abstract hierarchy, causes scaffolding to fail

[vslee]

Consider an interface which uses the default implementation feature on some temporary variables. Those temporary variables are marked with the [NotMapped] attribute. If _too many_ of those variables are used, and the interface is applied to an inheritance hierarchy which contains an _abstract_ ancestor, then the model is unable to scaffold. Please see the code example below:

```C#
using Microsoft.EntityFrameworkCore;
using System.ComponentModel.DataAnnotations.Schema;

namespace InterfaceOnDerived
{
class Program
{
static void Main(string[] args) { }
}
public class BloggingContext : DbContext
{
public DbSet BlogPosts { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(
            @"Server=(localdb)\mssqllocaldb;Database=Blogging;Integrated Security=True");
    }
}

public interface ITitle
{
    // commenting out one or more of these NotMapped properties fixes the problem
    [NotMapped] public string Temp1 => "abcd";
    [NotMapped] public string Temp2 => "abcd";
    [NotMapped] public string Temp3 => "abcd";
    [NotMapped] public string Temp4 => "abcd";
    [NotMapped] public string Temp5 => "abcd";

    public string Title { get; set; } // commenting out this property also fixes the problem
}

public abstract class Post : ITitle // making this non-abstract also fixes the problem
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public string Title { get; set; }

}
public class BlogPost : Post { }

}

PM> Add-Migration MyFirstMigration -v
Using project 'InterfaceOnDerived'.
Using startup project 'InterfaceOnDerived'.
Build started...
Build succeeded.
C:Program Filesdotnetdotnet.exe exec --depsfile "G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerivedbinDebugnet5.0InterfaceOnDerived.deps.json" --additionalprobingpath C:Usersvslee.nugetpackages --runtimeconfig "G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerivedbinDebugnet5.0InterfaceOnDerived.runtimeconfig.json" C:Usersvslee.nugetpackagesmicrosoft.entityframeworkcore.tools5.0.0toolsnetcoreapp2.0anyef.dll migrations add MyFirstMigration --json --verbose --no-color --prefix-output --assembly "G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerivedbinDebugnet5.0InterfaceOnDerived.dll" --startup-assembly "G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerivedbinDebugnet5.0InterfaceOnDerived.dll" --project-dir "G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerived\" --language C# --working-dir "G:Google DriveTestProjectsInterfaceOnDerived" --root-namespace InterfaceOnDerived
Using assembly 'InterfaceOnDerived'.
Using startup assembly 'InterfaceOnDerived'.
Using application base 'G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerivedbinDebugnet5.0'.
Using working directory 'G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerived'.
Using root namespace 'InterfaceOnDerived'.
Using project directory 'G:Google DriveTestProjectsInterfaceOnDerivedInterfaceOnDerived'.
Remaining arguments: .
Finding DbContext classes...
Finding IDesignTimeDbContextFactory implementations...
Finding application service provider in assembly 'InterfaceOnDerived'...
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 'BloggingContext'.
Microsoft.EntityFrameworkCore.Design.OperationException: Unable to create an object of type 'BloggingContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
---> System.TypeLoadException: Method 'set_Title' in type 'InterfaceOnDerived.BlogPost' from assembly 'InterfaceOnDerived, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.
at System.Signature.GetSignature(Void* pCorSig, Int32 cCorSig, RuntimeFieldHandleInternal fieldHandle, IRuntimeMethodInfo methodHandle, RuntimeType declaringType)
at System.Reflection.RuntimeMethodInfo.get_Signature()
at System.Reflection.RuntimeMethodInfo.FetchNonReturnParameters()
at System.Reflection.RuntimeMethodInfo.GetParametersNoCopy()
at System.Reflection.RuntimePropertyInfo.GetIndexParametersNoCopy()
at System.Reflection.RuntimePropertyInfo.GetIndexParameters()
at Microsoft.EntityFrameworkCore.Internal.DbSetFinder.<>c.b__2_0(PropertyInfo p)
at System.Linq.Enumerable.WhereArrayIterator1.ToArray() at System.Linq.Buffer1..ctor(IEnumerable1 source) at System.Linq.OrderedEnumerable1.GetEnumerator()+MoveNext()
at System.Linq.Enumerable.SelectIPartitionIterator2.LazyToArray() at System.Linq.Enumerable.SelectIPartitionIterator2.ToArray()
at System.Linq.Enumerable.ToArray[TSource](IEnumerable1 source) at Microsoft.EntityFrameworkCore.Internal.DbSetFinder.FindSetsNonCached(Type contextType) at System.Collections.Concurrent.ConcurrentDictionary2.GetOrAdd(TKey key, Func2 valueFactory) at Microsoft.EntityFrameworkCore.Internal.DbSetFinder.FindSets(Type contextType) at Microsoft.EntityFrameworkCore.Internal.DbSetInitializer.InitializeSets(DbContext context) at Microsoft.EntityFrameworkCore.DbContext..ctor(DbContextOptions options) at Microsoft.EntityFrameworkCore.DbContext..ctor() at InterfaceOnDerived.BloggingContext..ctor() --- End of stack trace from previous location --- at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.ConstructorMatcher.CreateInstance(IServiceProvider provider) at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, Object[] parameters) at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider provider, Type type) at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_4.<FindContextTypes>b__13() --- End of inner exception stack trace --- at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.<>c__DisplayClass13_4.<FindContextTypes>b__13() at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func1 factory)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
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.b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Unable to create an object of type 'BloggingContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
```

EF Core version: 5.0 RTM
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 5.0 RTM
Operating system: Windows 10 Pro 20H2
IDE: Visual Studio 2019 16.8.0

[vslee]

I also tried removing only the [NotMapped] attributes but leaving the default properties there, but that does not fix the problem.
Doing any of the three things in the code comments does, however.

[smitpatel]

Error is not related to EF Core at all. It happens without EF Core too.
Repro
```C#
using System;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Reflection;

namespace BugInReflection
{
class Program
{
static void Main(string[] args)
{
var p = typeof(Program).GetProperties().Select(e => e.GetIndexParameters()).ToList();
}

    public BlogPost BlogPost { get; set; }
}

public interface ITitle
{
    // commenting out one or more of these NotMapped properties fixes the problem
    [NotMapped] public string Temp1 => "abcd";
    [NotMapped] public string Temp2 => "abcd";
    [NotMapped] public string Temp3 => "abcd";
    [NotMapped] public string Temp4 => "abcd";
    [NotMapped] public string Temp5 => "abcd";

    public string Title { get; set; } // commenting out this property also fixes the problem
}

public abstract class Post : ITitle // making this non-abstract also fixes the problem
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public string Title { get; set; }

}
public class BlogPost : Post { }

}
```

[vslee]

Thank you for the quick response and debugging to figure out that the bug is external to EF Core. I should have dug deeper myself. I have now filed a bug in the appropriate repo https://github.com/dotnet/runtime/issues/44533.