How to fix issue with group join in linq / lambda expression? - linq

Question

I have the following Linq/Lambda expression to associate COMMENTS and ATTACHMENTS to RECORDS (these are the names of tables in database).
var comments = repositoryBase.Query<Comments>()
.Select(x => x);
var attachments = repositoryBase.Query<Attachment>()
.Where(x => x.DeletedFlag == false)
.Select(x => x);
var recordItems = repositoryBase.Query<Record>()
.Where(x => x.DepartmentId == departmentIdId && x.DeletedFlag == false);
recordItems = recordItems
.Where(x => x.Featured == true && (x.PhaseTypeId == 2 || x.PhaseTypeId == 3)); // filtering
var recordComments = recordItems
.GroupJoin(comments,
itm => new { a = 1, b = itm.RecordId },
c => new { a = c.TypeId, b = c.Id },
(itm, c) => new { c, itm })
.SelectMany(x => x.c.DefaultIfEmpty(), (x, y) => new
{
Comments = (y != null) ? true : false,
CommentsCount = x.c.Count(),
RecordId = x.itm.RecordId,
Featured = x.itm.Featured,
Id = x.itm.RecordId,
PhaseName = x.itm.PhaseType.PhaseName,
x.itm.ProductionDate,
x.itm.PublishedDate,
Title = x.itm.RecordTitle,
x.itm.UpdatedDate
}).Distinct();
where TypeId and Id in c => new { a = c.TypeId, b = c.Id } are fields in comments on which the group join(left outer join) is done.
var recordAttachments = recordComments
.GroupJoin(attachments,
itm => new { a = 1, b = itm.RecordId },
at => new { a = at.ContentType, b = at.ContentId },
(itm, at) => new { at, itm})
.SelectMany(x => x.at.DefaultIfEmpty(), (x, y) => new
{
Attachments = (y != null) ? true : false,
AttachmentsCount = x.at.Count(),
AttachmentTitle = y.FileName,
AttachmentId = (y != null) ? y.AttachmentId : 0,
TypeId = (y != null) ? y.ContentType : 0,
ItemId = (y != null) ? y.ContentId : 0,
Comments = x.itm.Comments,
CommentsCount = x.itm.CommentsCount,
Featured = x.itm.Featured,
Id = x.itm.RecordId,
PhaseName = x.itm.PhaseName,
x.itm.ProductionDate,
x.itm.PublishedDate,
Title = x.itm.Title,
x.itm.UpdatedDate
}).Distinct().ToList();
But with the last lambda expression there is an issue that if there are two attachment for the same record, the record with attachment gets duplicated (not in database but in view).
As shown here
"Data": [
{
"typeid": 1,
"typename": "Record Scan",
"id": 3071,
"title": "Late Outcomes",
"publishdate": "3/4/2013",
"featured": true,
"productiondate": "",
"phasename": "Board",
"updateddate": "4/29/2013",
"updateddateforsorting": "2013-04-29T19:44:29.47",
"comments": true,
"numofcomments": 4,
"attachment": true,
"numofattachments": 2,
"attachments": [
{
"attachmentid": 371,
"typeid": 1,
"id": 0,
"title": "Cardio_David.docx",
"name": null,
"createddate": "0001-01-01T00:00:00"
},
{
"attachmentid": 434,
"typeid": 1,
"id": 0,
"title": "blanks in password field.docx",
"name": null,
"createddate": "0001-01-01T00:00:00"
}
]
},
{
"typeid": 1,
"typename": "Record Scan",
"id": 3071,
"title": "Late Outcomes",
"publishdate": "3/4/2013",
"featured": true,
"productiondate": "",
"phasename": "Board",
"updateddate": "4/29/2013",
"updateddateforsorting": "2013-04-29T19:44:29.47",
"comments": true,
"numofcomments": 4,
"attachment": true,
"numofattachments": 2,
"attachments": [
{
"attachmentid": 371,
"typeid": 1,
"id": 0,
"title": "Cardio_David.docx",
"name": null,
"createddate": "0001-01-01T00:00:00"
},
{
"attachmentid": 434,
"typeid": 1,
"id": 0,
"title": "blanks in password field.docx",
"name": null,
"createddate": "0001-01-01T00:00:00"
}
]
}
]
NB- this is a sample data ignore the field names and values
I 've editted the last code recordAttachment as
var recordAttachment= from rc in recordComments
join at in attachments on rc.RecordId equals at.ContentId into ra
select new { Comments = rc.Comments, CommentsCount = rc.CommentsCount Featured = rc.Featured, Id = rc.RecordId, PhaseName = rc.PhaseName, rc.ProductionDate, jac.PublishedDate, Source = jac.Source, Title = rc.Title, rc.UpdatedDate, AttachmentCount = ra.Count(), Attachments = ra, IsAttachment = (ra.Count() != null) ? true : false };
This returns record and associated attachments. Now i need to Map this data to a view model..
public class FlaggedItemModel
{
public int typeid { get; set; }
public string typename { get; set; }
public int id { get; set; }
public string title { get; set; }
public string publishdate { get; set; }
public bool featured { get; set; }
public string productiondate { get; set; }
public string phasename { get; set; }
public string updateddate { get; set; }
public DateTime updateddateforsorting { get; set; }
public bool comments { get; set; }
public int numofcomments { get; set; }
public bool attachment { get; set; }
public int numofattachments { get; set; }
public IList<AttachmentModel> attachments { get; set; }
}
I tried this code but not working
var recordlist = journalArticleAttachments.Select(x => new FlaggedItemModel() { attachments = x.Attachments.Where(z => z.ContentId == x.Id).Select(jaa => new AttachmentModel() { attachmentid = jaa.AttachmentId, typeid = jaa.ContentType, title = jaa.FileName }).ToList(), numofcomments = x.CommentsCount, comments = x.Comments, featured = x.Featured, id = x.Id, phasename = x.PhaseName, productiondate = (x.ProductionDate.HasValue) ? x.ProductionDate.Value.ToShortDateString() : string.Empty, publishdate = (x.PublishedDate.HasValue) ? x.PublishedDate.Value.ToShortDateString() : string.Empty, title = x.Title, typeid = 1, typename = "Journal Scan", updateddate = x.UpdatedDate.ToShortDateString(), updateddateforsorting = x.UpdatedDate });
How to fix this issue?

Answer 1

You are getting this error because you are trying to get the database to convert a datetime to a formatted short date string, which it doesn't know how to do. I would recommend changing your model to have a production date be a datetime field, and formatting it appropriately in your view. Changing the datetime to a string in the controller (or DAL) isn't the appropriate place to do it.
Alternatively, if you insist on having the shortdate in your viewmodel, have the query initally return the field as date time, then call .ToList() on the query, and then project that result into your final view so that the result will be returned from the database as datetime, and then you can have it convert it to shortdate in C#. Something like this:
var recordlist = journalArticleAttachments.Select(x=>new { ..., publishdate, ...}).ToList().Select(x=>new { ..., publishdate = (publishdate==null) ? publishdate.ToShortDateString() : string.Empty, ...});