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How to take top 3 elements in each group using Entity Framework

I have the data in the source table.
And I want to get this kind of result in list using lambda expression and Entity Framework. I don't know how to do it. I need to get top 3 rows in for each CategoryId.
Probably using something like this:
context.GroupBy(x => x.CategoryId)
.Select(group => new {
CategoryId = group.Key,
NameId = group.Select(x => x.NameId),
group.OrderByDescending(e => e.Count).Take(3)
})
.ToListAsync()

var list = context
.GroupBy(x => x.CategoryId)
.SelectMany(group => group.OrderByDescending(e => e.Count).Take(3))
.OrderByDescending(e => e.Count)
.ToListAsync();
If you want an anonymous type:
var list = context
.GroupBy(x => x.CategoryId)
.SelectMany(group => group.OrderByDescending(e => e.Count).Take(3))
.Select(x => new
{
x.CategoryId,
x.NameId,
x.Count
})
.OrderByDescending(x => x.Count)
.ToListAsync();

Using LINQ ANY and occurrence > 1

I have a list of objects containing a collection of child objects. I want to check if any of these objects children contain a specific value AND if they do then check if this value appears in any other objects.
I currently have this which needs to be extended for the second check:
public bool HasAnyTypesMoreThanOnce(IEnumerable<Parent> parents, IEnumerable<string> Types)
{
return parents
.SelectMany(p => p.Children)
.Any(c => Types.Contains(c.Type));
}
I was thinking of something like this:
var list = parents
.SelectMany(p => p.children)
.Where(c => Types.Contains(c.Type))
.Select(c => c.Type).ToList();
return list.Count != list.Distinct().Count();
Any suggestions?

Another approach would be to group by Type and return true if theres any Type repeating more than once otherwise false.
return parents.SelectMany(p => p.children)
.Where(c => Types.Contains(c.Type))
.GroupBy(x => x.Type)
.Any(g => g.Count() > 1);

Maybe something like this
parents
.GroupBy(c => c.children.type)
.Where(grp => grp.Count() > 1)
.Select(grp => grp.children.type);

EF 6 complex query with Include not including relations

i have a somewhat complex structure i wont get into,
but what i try doing is:
Get all ShopItems, who's SourceItem has changed,
Get and update them according to their Source/Shop data.
i conjured the following:
var query = _ctx.ShopItems
.Include(si => si.Shop)
.Include(si=>si.SourceItem)
.Include(si => si.SourceItem.Source)
.Include(si=>si.Shop.ShopType)
.GroupBy(i => i.SourceItem)
.Where(g => g.Key.LastUpdate > lastUpdate)
.OrderBy(g => g.Key.LastUpdate)
.Take(updateCountLimit);
the query seems to work, but when itterating the Groups:
groupItem.Key.Source is null.
I somewhat solved it by Removing the Include()s, saving the Entities to an Array, and explicitly loading the references using
_ctx.Entry(updatedSourceItem.Key).Reference(src=>src.Source).Load();
How can i perform the query i want without round-tripping the DB for explicit loading ?

Not sure, but it's backwards to start with ShopItems and then group by SourceItem. Try just starting with SourceItem, something like
:
var query = _ctx.SourceItems
.Include(i => i.ShopItems)
.Include(i => i.Source)
.Include(i => i.ShopItems.Select( si => si.Shop))
.Include(i => i.ShopItems.Select( si => si.Shop).ShopType)
.Where(i => i.LastUpdate > lastUpdate)
.OrderBy(i => i.LastUpdate)
.Take(updateCountLimit);
//or
var query = _ctx.SourceItems
.Include("ShopItems")
.Include("Source")
.Include("ShopItems.Shops")
.Include("ShopItems.Shops.ShopType")
.Where(i => i.LastUpdate > lastUpdate)
.OrderBy(i => i.LastUpdate)
.Take(updateCountLimit);

automapper optimization mapping (model to view model -> get latest version)

I am trying to optimize this part of code:
Mapper.CreateMap<Document, DocumentViewModel>()
.ForMember(g => g.Id, map => map.MapFrom(d => d.documentVersion.Where(v => v.version == d.documentVersion.Select(s => s.version).Max()).OrderByDescending(s => s.subVersion).First().Id))
.ForMember(g => g.IdRootDocument, map => map.MapFrom(d => d.Id))
.ForMember(g => g.certyficateType, map => map.MapFrom(d => d.documentVersion.Where(v => v.version == d.documentVersion.Select(s => s.version).Max()).OrderByDescending(s => s.subVersion).First().certyficateType))
I'm Using automapper, and I'm trying to optimize this part of code
In this part I'm trying mapping object from document to documentViewModel, in this complex model, source data always will be latest document version:
d => d.documentVersion.Where(v => v.version == d.documentVersion.Select(s => s.version).Max()).OrderByDescending(s => s.subVersion).First().myProportyX
Could anyone offer an example or suggestion as to how to approach optimization in this situation?

d => d.documentVersion.Where(v => v.version == d.documentVersion.Select(s => s.version).Max()).OrderByDescending(s => s.subVersion).First().myProporty
You are iterating quite a few times here, you may consider doing something like:
d.documentVersion.OrderByDescending(v => v.version).ThenByDescending(v => v.subVersion).First().myProperty
to reduce the number of iterations and only get the top version/subversion.

optimization mapping:
Mapper
.CreateMap<Document, DocumentViewModel>()
.ConvertUsing(doc =>
{
DocumentViewModel result = new DocumentViewModel();
DocumentVersion lastVersion = doc.documentVersion.Where(v => v.version == doc.documentVersion.Select(s => s.version).Max()).OrderByDescending(s => s.subVersion).First();
Mapper.Map(lastVersion, result);
return result;
});

Loading all the children entities with entity framework

I have a data model like this
I would like to load all the related entities from a Reconciliation into a Reconciliation object.
For now the only way I could find to load all the related entites to a single Recon is in multiple Lists. But I want to load every related entities in a Reconciliation object. If possible in an elegant way.
Reconciliation recon = db.Reconciliations
.Where(r => r.ReconNum == 382485).First();
List<ReconciliationDetail> reconDetails = recon.ReconciliationDetails.ToList();
List<JrnlEntryDetail> jrnlDetails = reconDetails.Select(r => r.JrnlEntryDetail).ToList();
List<JrnlEntry> jrnl = jrnlDetails.Select(j => j.JrnlEntry).ToList();
List<ARInvoice> invoices = jrnl.SelectMany(j => j.ARInvoices).ToList();
List<ARInvoiceDetail> invoicesDetail = invoices
.SelectMany(i => i.ARInvoiceDetails).ToList();
List<ARCredMemo> credmemos = jrnl.SelectMany(j => j.ARCredMemoes).ToList();
List<ARCredMemoDetail> credmemosDetail = credmemos
.SelectMany(c => c.ARCredMemoDetails).ToList();
List<IncomingPay> incomingPays = jrnl.SelectMany(j => j.IncomingPays).ToList();
List<IncomingPayDetail> incomingPaysDetail = incomingPays
.SelectMany(i => i.IncomingPayDetails).ToList();
// ... and so on for outgoing pays, AP Invoices AP Cred Memo ...etc
I have also tried to load it with Include and Select but I get this exception :
The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties.
And I don't get how I could load every childs of JrnlEntry using Include and Select
Reconciliation recon = db.Reconciliations
.Where(r => r.ReconNum == 382485)
.Include(r => r.ReconciliationDetails
.Select(d => d.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry)
.SelectMany(j => j.ARInvoices).SelectMany(i => i.ARInvoiceDetails))
Edit
Managed to do it this way too but it's not very beautiful :
Reconciliation recon = db.Reconciliations
.Where(r => r.ReconNum == 382485)
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.ARInvoices.Select(i => i.ARInvoiceDetails)))
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.ARCredMemoes.Select(c => c.ARCredMemoDetails)))
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.IncomingPays.Select(i => i.IncomingPayDetails)))
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.OutgoingPays.Select(o => o.OutgoingPayDetails)))
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.APInvoices.Select(o => o.APInvoiceDetails)))
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.APCredMemoes.Select(o => o.APCredMemoDetails)))
.Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
.Select(jd => jd.JrnlEntry).Select(j => j.JrnlEntryDetails))

There are two ways to perform Eager Loading in Entity Framework:
ObjectQuery.Include Method
Explicit loading using either DbEntityEntry.Collection Method or DbEntityEntry.Reference Method along with their respective Load methods
There are also manners to write Raw SQL Queries against database:
DbSet.SqlQuery Method deals with entities
Database.SqlQuery Method deals with arbitrary types
Database.ExecuteSqlCommand Method for arbitrary DDL/DML
For the case, when you're attempting to load nearly entire database, it would be good idea to execute dedicated store procedure against it.

Try with just .Include(r => r.ReconciliationDetails) initially. Then add the .Select() statements one-by-one. At what point does the exception reappear? The .SelectMany() call looks a bit suspicious to me!
A second question that might help identify the problem... After you run the code that contains all the ToList() calls, is your recon entity complete? i.e. are all its navigation properties populated? This should be the case because of the automatic 'fixup' behavior of Entity Framework.
With EF, sometimes it is more efficient to load a complex object graph with several calls rather than chained Include() calls. Check the generated SQL and see what is most efficient in your case.

Not sure if it's to late but could you benefit from structuring your code such as
var acctName = "someName";
var detailList = _repository.Include(e => e.JrnlEntryDetail).Filter(c => c.JrnlEntryDetail.Any(e => e.AcctName == acctName)).Get().ToList();