LINQ GroupBy throwing errors

Question

 var devSum = repository.Devices
                    .Where(dev => dev.Id == deviceId)
                    .Join(repository.ManagementGroups, device => device.ManagementGroupId, mGroup => mGroup.Id, (device, mGroup) => new { device, mGroup.Name })
                    .Join(repository.DataGroups, device_mGroup => device_mGroup.device.DataGroupId, dGroup => dGroup.Id, (device_mGroup, dGroup) => new { device_mGroup.device, managerName = device_mGroup.Name, dataName = dGroup.Name })
                    .Join(repository.DeviceTypes, d => d.device.TypeId, t => t.Id, (d, t) => new { d.device, d.dataName, d.managerName, TypeName = t.Name })
                    .SingleOrDefault();

Hi, I have the above query joining several tables and all was working. Then I realised some of the foreign keys may be empty.

I've researched the use of GroupBy and DefaultIfEmpty, and they sounded promising so I tried changing the first Join to GroupJoin on but this threw an error:

 var devSum = repository.Devices
                    .Where(dev => dev.Id == deviceId)
                    .GroupJoin(repository.ManagementGroups, device => device.ManagementGroupId, mGroup => mGroup.Id, (device, mGroup) => new { device, mGroup.Name })
                    .Join(repository.DataGroups, device_mGroup => device_mGroup.device.DataGroupId, dGroup => dGroup.Id, (device_mGroup, dGroup) => new { device_mGroup.device, managerName = device_mGroup.Name, dataName = dGroup.Name })
                    .Join(repository.DeviceTypes, d => d.device.TypeId, t => t.Id, (d, t) => new { d.device, d.dataName, d.managerName, TypeName = t.Name })
                    .SingleOrDefault();

'AnonymousType#1' does not contain a definition for 'Name' and no extension method 'Name' accepting a first argument of type 'AnonymousType#1' could be found (are you missing a using directive or an assembly reference?)

Can anyone help please?

Added my edited code, the error is on the line with .GroupJoin at the end of the line where it tries to get mGroup.Name — DavidB, Mar 04 '13 at 15:52

score 3 · Accepted Answer · answered Mar 04 '13 at 15:57

3

mGroup in the line (device, mGroup) => new { device, mGroup.Name } actually represents the whole collection. You'd need to do a Select on it:

(device, mGroup) => new { Device = device, NameGroup = mGroup.Select(m => m.Name) }

Check out the MSDN page on GroupJoin for more info.

answered Mar 04 '13 at 15:57

Corey Adler

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thankyou IronMan, but that throws the error Error 17 Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access. – DavidB Mar 04 '13 at 15:59
1

Looks like the MSDN has that in their example. I've edited my answer accordingly. – Corey Adler Mar 04 '13 at 16:00
1

thanks, Thats got rid of the errors on that line at least! Ill keep fiddling to try and correct the rest myself and come back and accept this answer when i do. – DavidB Mar 04 '13 at 16:03
1

The other errors were just chnagign the names on the second line as they had changed on the first. Thanks for your help pal. – DavidB Mar 04 '13 at 16:09
No problem. Good luck to you on your project. – Corey Adler Mar 04 '13 at 16:14

LINQ GroupBy throwing errors

1 Answers1