Performing a join on a group by linq

Question

I'm trying to perform a group by and then a join after (based on what other posts here suggested) and i'm getting the following error in .NET 5

'RelationalProjectionBindingExpressionVisitor' failed. This may indicate either a bug or a limitation in Entity Framework.

code:

var test = (from ra in _db.ResourceAllocation
                        group ra by new { ra.Date, ra.ResourceId } into g
                        join resource in _db.Resource on g.Key.ResourceId equals resource.Id
                        select new
                        {
                            ResourceName =  resource.Name,
                            ResourceDayOfWeek = resource.DayOfWeek,
                            g.Key.Date,
                            userSum = g.Sum(x => x.userCount)
                        }).OrderByDescending(e => e.Date).ToList();

Answer 1

Try to simplify life for LINQ Translator and separate queries by parts. This query should be translatable:

var grouped = 
    from ra in _db.ResourceAllocation
    group ra by new { ra.Date, ra.ResourceId } into g
    select new 
    {
        g.Key.Date,
        g.Key.ResourceId,
        userSum = g.Sum(x => x.userCount)
    }

var query =
    from g in grouped
    join resource in _db.Resource on g.ResourceId equals resource.Id
    select new
    {
        ResourceName = resource.Name,
        ResourceDayOfWeek = resource.DayOfWeek,
        g.Date,
        g.userSum
    );
    
var result = query.OrderByDescending(e => e.Date).ToList();