Empty DbSet throw System.NullReferenceException when accessed even with SingleOrDefault and similar

[salaros]

In previous stable EF Core version (2.2.6) DbSets behaved differently. One could call SingleOrDefault/SingleOrDefaultAsync (both parameter-less and with a predicate) on an empty DbSet without raising System.NullReferenceException.
My tests in this solution demonstrate it.

Steps to reproduce

Please take a look EmptyDbSet project in this solution and InMemoryTests.EmptyDbSet() xUnit test.

db.Set<MyEntity>().SingleOrDefault();

Further technical details

EF Core version: 3.0.0-preview7.19362.6
Database Provider: Microsoft.EntityFrameworkCore.InMemory
Operating system: any
IDE: Visual Studio 2019 16.2

[ajcvickers]

Note for triage: repos in current nightly:

Unhandled exception. System.InvalidOperationException: Operation is not valid due to the current state of the object.
   at Microsoft.EntityFrameworkCore.InMemory.Query.Internal.InMemoryProjectionBindingExpressionVisitor.VisitExtension(Expression extensionExpression)
   at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.InMemory.Query.Internal.InMemoryProjectionBindingExpressionVisitor.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.InMemory.Query.Internal.InMemoryProjectionBindingExpressionVisitor.Translate(InMemoryQueryExpression queryExpression, Expression expression)
   at Microsoft.EntityFrameworkCore.InMemory.Query.Internal.InMemoryQueryableMethodTranslatingExpressionVisitor.TranslateSelect(ShapedQueryExpression source, LambdaExpression selector)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass12_0`1.<ExecuteAsync>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ExecuteAsync[TSource,TResult](MethodInfo operatorMethodInfo, IQueryable`1 source, Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ExecuteAsync[TSource,TResult](MethodInfo operatorMethodInfo, IQueryable`1 source, LambdaExpression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.SingleOrDefaultAsync[TSource](IQueryable`1 source, Expression`1 predicate, CancellationToken cancellationToken)
   at Program.Main() in C:\Stuff\ThreeOhP7P\ThreeOhP7P\Program.cs:line 322
   at Program.<Main>()

[Owned]
public class OwnedModel
{
    [Column(nameof(RequiredField))]
    [Required]
    public string RequiredField { get; set; }
}

public class DummyModel
{
    [Required]
    [Key, Column(Order = 0)]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long Id { get; set; }

    [Required]
    public OwnedModel OwnedModel { get; set; }
}

public class BloggingContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder.UseInMemoryDatabase("Test");

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder
            .Entity<DummyModel>()
            .HasKey(d => d.Id);
    }
}

public class Program
{
    public static async Task Main()
    {
        using (var context = new BloggingContext())
        {
            context.Database.EnsureDeleted();
            context.Database.EnsureCreated();
        }

        using (var context = new BloggingContext())
        {
            var id = 1;

            var results = await context.Set<DummyModel>().SingleOrDefaultAsync(d => id == d.Id);
        }
    }
}

[smitpatel]

There is owned entity which will generate eager loaded include. Includes are not working for InMemory yet.

[ajcvickers]

@smitpatel Which issue is tracking that?

[smitpatel]

#15711

[ajcvickers]

@smitpatel Should have guessed...but we might need something specific in 3.0.

[ajcvickers]

Created #16963 to track this in 3.0.