SelectMany in Preview 8

[JonathanMagnan]

Describe what is not working as expected.

SelectMany in preview 8 doesn't work anymore with some basic query such

context.Invoices.SelectMany(x => x.Items).ToList();

If you are seeing an exception, include the full exceptions details (message and stack trace).

Exception message: The method or operation is not implemented.
Stack trace:
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.TranslateSelectMany(ShapedQueryExpression source, LambdaExpression selector)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.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__DisplayClass9_0`1.<Execute>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.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetEnumerator()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Z.Test.EntityFramework.Plus.QueryIncludeFilter_FirstWithPredicate.Many_Executor() in C:\Users\Jonathan\Desktop\Z\TFS\EFPlus\Z.EntityFramework.Plus\Z.Test.EntityFramework.Plus.EFCore.Shared\QueryIncludeFilter\FirstWithPredicate\Many_Executor.cs:line 25

Steps to reproduce

Include a complete code listing (or project/solution) that we can run to reproduce the issue.

Partial code listings, or multiple fragments of code, will slow down our response or cause us to push the issue back to you to provide code to reproduce the issue.

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Data.SqlClient;
					
public class Program
{
	public static void Main()
	{
		using (var context = new EntityContext())
		{
			context.Database.EnsureCreated();
			var list = context.Invoices.SelectMany(x => x.Items).ToList();
		}
	}

	public class EntityContext : DbContext
	{
		public EntityContext() 
		{
		}

		protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
		{
			optionsBuilder.UseSqlServer(new SqlConnection("[ConnectionString]"));

			base.OnConfiguring(optionsBuilder);
		}
		
		public DbSet<Invoice> Invoices { get; set; }
		public DbSet<InvoiceItem> InvoiceItems { get; set; }
	}

	public class Invoice
	{
		public int InvoiceID { get; set; }
		public string Number { get; set; }
		
		public List<InvoiceItem> Items { get; set; }
	}
	
	public class InvoiceItem
	{
		public int InvoiceItemID { get; set; }
		public string ProductName { get; set; }
		public Invoice Invoice { get; set; }
	}
}

You can try the online fiddle for v2.x which work fine: https://dotnetfiddle.net/QkOkj0

Further technical details

EF Core version: 3.0.0-preview8.19405.11
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows
IDE: Visual Studio 2019 16.2.2

[ajcvickers]

Duplicate of #15711. Verified fixed on current daily build.