Query exception after upgrading from 6.0.1 to 6.0.2

[MariovanZeist]

After upgrading all packages to 6.03 I have a query that fails.
(Problem also occurs when upgrading from 6.0.1 to 6.0.2)

I have the following query (The DbContext is the default IdentityDbContext)
(The query gets the user roles from the user)

var roles = await ctx.Users.Where(u => u.Id == userId).Select(u => u.Roles.Select(r => r.Name)).FirstOrDefaultAsync();

in 6.0.1 it returns an IEnumerable<string> containing the roles
in 6.0.3 (and 6.0.2) it generates an exception:

Expression of type 'System.Threading.Tasks.Task`1[System.Collections.Generic.List`1[System.String]]' cannot be used for return type 'System.Threading.Tasks.Task`1[System.Collections.Generic.IEnumerable`1[System.String]]'"}

with the following stacktrace:

   at System.Linq.Expressions.Expression.ValidateLambdaArgs(Type delegateType, Expression& body, ReadOnlyCollection`1 parameters, String paramName)
   at System.Linq.Expressions.Expression.Lambda[TDelegate](Expression body, String name, Boolean tailCall, IEnumerable`1 parameters)
   at System.Linq.Expressions.Expression.Lambda[TDelegate](Expression body, Boolean tailCall, IEnumerable`1 parameters)
   at System.Linq.Expressions.Expression.Lambda[TDelegate](Expression body, ParameterExpression[] parameters)
   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.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, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.FirstOrDefaultAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)

To reproduce:
https://github.com/MariovanZeist/EFCoreTest

and follow the readme

I am (trying) to use EF Core 6.03
Database provider: (e.g. Microsoft.EntityFrameworkCore.SqlServer)
Target framework: (e.g. .NET 6.0)
Operating system: Windows VS 2022 (17.1)

[maumar]

@MariovanZeist In order to fix the problem add ToList to the collection inside the projection:

var roles = await ctx.Users.Where(u => u.Id == Guid.NewGuid()).Select(u => u.Roles.Select(r => r.Name).ToList()).FirstOrDefaultAsync();

[MariovanZeist]

Thanks @maumar
I ended up using

  var roles = await ctx.Users.Where(u => u.Id == userId).SelectMany(u => u.Roles.Select(r => r.Name)).ToListAsync();

But I have several more queries that fail after the upgrade so I was forced to revert back to 6.0.1.

[MariovanZeist]

I can circumvent the problem by adding

  AppContext.SetSwitch("Microsoft.EntityFrameworkCore.Issue27105", true);

To my startup code

I believe the problem has been introduced here: #27134

So I will test to see if this alleviates my problems, so I can upgrade to 6.0.3.

[mattfrear]

Just chiming in to say that I also had this issue, and confirming that it is now fixed in the 6.0.5 release.

System.ArgumentException: Expression of type 'Task<List<MyType>>' cannot be used for return type 'Task<IEnumerable<MyType>>'

I didn't find this issue sooner because it doesn't mention ArgumentException and that is what I was searching google and GitHub for.