[jcouv summary:] requesting support for await in expression trees.

@lillo42 commented on Wed Dec 19 2018

I'm studying C# 8 and new we have a new interface call IAsyncEnumerable and I was think maybe it's a good ideia create a new interface call IAsyncQueryable to be possible using await foreach async with ORM like EF or NHibernarte:

IAsyncQueryable query = database.Where(...);

await foreach(var a in query) {
...
}

I was thinking IAsyncQueryable could be:

public interface IAsyncQueryable : IAsyncEnumerable
{
   Type ElementType { get; }
    Expression Expression { get; }
    IQueryProvider Provider { get; }
}


public interface IAsyncQueryable<T> : IAsyncQueryable, IAsyncEnumerable<T>
{

}

or

public interface IAsyncQueryable : IQueryable, IAsyncEnumerable
{

}


public interface IAsyncQueryable<T> : IQueryable<T>, IAsyncQueryable,  IAsyncEnumerable<T>
{

}

@Suchiman commented on Wed Dec 19 2018

Since IQueryable is about composing a query rather than constructing an execution pipeline, it would probably make more sense to follow the current Approach (used by EF) of adding an extension like this

public static IAsyncEnumerable<TSource> AsAsyncEnumerable<TSource>(this IQueryable<TSource> source)

@quinmars commented on Thu Dec 20 2018

The async enumerable implementation is developed in the dotnet/reactive repo. And there actually is already an IAsyncQueryable interface:

https://github.com/dotnet/reactive/blob/IxAsyncCSharp8/Ix.NET/Source/System.Linq.Async.Queryable/System/Linq/IAsyncQueryable.cs

@tarekgh commented on Thu Jan 17 2019

cc @stephentoub

@stephentoub commented on Thu Jan 17 2019

Without language support for awaits in expression trees, I don't think there's much that can or should be done here.
cc: @cston, @jaredpar

@jaredpar commented on Thu Jan 17 2019

I agree. There is currently no plans to invest in our expression tree support at this time.

@tarekgh commented on Thu Jan 17 2019

@jaredpar should we move this issue to your repo you may track it for the future if anything change?

@jaredpar commented on Thu Jan 17 2019

Either way. This is one of those features that crosses our repositories so I'm fine with it being here or there.

@tarekgh commented on Thu Jan 17 2019

Thanks @jaredpar I'll move it because corefx can support it if the it is decided from your side to support it.