How to write group join query in Entity Framewok Core 3.1

Question

When I write the linq query like this, I get the error message

"System.InvalidOperationException: 'The LINQ expression 'DbSet() .GroupJoin( inner: DbSet(), outerKeySelector: d => d.Id, innerKeySelector: dc => dc.DeviceId, resultSelector: (d, dc) => new { deviceName = d.Name, cams = dc })' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.'

How should I edit the code?

var query = context.Devices
                   .GroupJoin(context.DeviceControls,
                              d => d.Id,
                              dc => dc.DeviceId,
                              (d, dc) => new
                                         {
                                             deviceName = d.Name,
                                             Cams = dc,
                                         }).ToList();

Don't join, use a navigation property. – Gert Arnold Feb 14 '22 at 19:58 — Gert Arnold, Feb 14 '22 at 19:58

score 2 · Accepted Answer · answered Feb 14 '22 at 19:39

2

EF core with .net core 3.1 will not let you do group by unless you do it client side. You need to call var query = context.Devices.ToList() and then do your group call on the query variable. Another option, if possible, is upgrading to .net 6. I think then you can do a server side group by.

answered Feb 14 '22 at 19:39

rleffler

430
6
15

Thank you for answer .my problem was resolved when i did query = context.Devices.ToList() – Feb 14 '22 at 20:11

How to write group join query in Entity Framewok Core 3.1

1 Answers1