Translate as in where clause

[Anduin2017]

I have two class:

public abstract class Conversation
{
    public int Id { get; set; }
}

public class PrivateConversation : Conversation
{
    public ICollection<User> Users { get; set; }
}

In DbContext, there are DbSets:

public DbSet<Conversation> Conversations { get; set; }
public DbSet<PrivateConversation> PrivateConversations { get; set; }
public DbSet<User> Users { get; set; }

Which generates two tables: Conversations and Users.

PrivateConversations are saved in table Conversations

Now an error occurred with query:

// For some reason, I can only query `db.Conversations`, can not access `db.PrivateConversations`
var conversations = db.Conversations
  .Include(t => (t as PrivateConversation).Users)
  .Where(t => t is PrivateConversation)
  .Where(t => (t as PrivateConversation).Users.Any())
  .ToList();

Told me that in Users.Any(), Users is null.

I am very confused. How can I query all private conversations with user in it?

Additional info:

packages I usesd:

<PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="2.2.6" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SQLServer" Version="2.2.6" />

runtime: .NET Core 2.2

<OutputType>Exe</OutputType>
<TargetFramework>netcoreapp2.2</TargetFramework>

[ajcvickers]

@Anduin2017 EF translates .Where(t => ((PrivateConversation)t)... but not .Where(t => (t as PrivateConversation)....

[Anduin2017]

Thanks! That really solves!

[Anduin2017]

Ok. I gotta be really happy if you can fix this and translate the as grammar.

[SARAVANA1501]

Can you tell me where I can add this new grammar?

[ajcvickers]

@smitpatel Since you added good-first-issue here can you point @SARAVANA1501 in the right direction to submit a PR for this?

[smitpatel]

While code is similar in various place, we can start with one location and update at all location once the structure is define.

https://github.com/aspnet/EntityFrameworkCore/blob/b7df776b0e1b2d94da48b0471c657fda8dbe8f9b/src/EFCore/Query/Internal/NavigationExpandingExpressionVisitor.ExpressionVisitors.cs#L90-L102

Above code basically unwrap a convert node and gives the converted type. Similar to above processing it needs to identify TypeAsOperation and then unwrap it to identify converted type and innerExpression. It should be added as extension method so all places can easily utilize it. So it goes this way.

Expression	Inner	ConvertedType
a.Property	a	null
((T)a).Property	a	T
(a as T).Property	a	T

[smitpatel]

This is already fixed in master branch in #19377