I'm trying to order the values in a related table using LINQ to SQL.
I have 2 tables. Menu and MenuSection. They are related one to many on Menu.MenuId == MenuSection.MenuId
Currently, I'm pulling this information using the following query
var menus = from m in _context.Menus
select m;
This gets fed into an ASP.NET MVC page and works fine.
I'd like to be able to sort the data the column MenuSection.Order
I've tried doing this:
var menus = from m in _context.Menus
join ms in _context.MenuSections on m.MenuId equals ms.MenuId
orderby ms.Order ascending select m;
But it's bringing back a set of data that is incorrect. It displays repeated Menu information.
EDIT: To clarify what i'm expecting the data shoud be:
There are x Menu's in Menu.
Each Menu has many MenuSection's
I'd like to list out each Menu and their related MenuSection.
The MenuSections need to be in order based on MenuSection.Order
Menu 1
- MenuSection 1, Order = 1
- MenuSection 3, Order = 2
Menu 2
- MenuSection 4, Order = 1
- MenuSection 2, Order = 2
Round 3: That last revision to the question clarifies it a lot. It sounds like what you really need is a group-by. Those are harder to get right without the IntelliSense but I'll try my best:
var groupings =
from m in _context.Menus
orderby m.Foo
from ms in m.MenuSections
orderby ms.Order
group ms by m;
foreach (var group in groupings)
{
Menu menu = group.Key;
// use the Menu
foreach (MenuSection ms in group)
{
// use the MenuSection
}
}
Now I added an extra orderby m.Foo where Foo is some property that I think you might want on Menu. Otherwise you aren't guaranteed to know the order of the top level menus.
Also note what I was saying earlier that the m.MenuSections is really a helper that is similar to from ms in _context.MenuSections where ms.MenuId == m.MenuId.
have you tried something like this? ...
var menus = (from m in _context.Menus
join ms in _context.MenuSections on m.MenuId equals ms.MenuId
orderby ms.Order ascending select m).Distinct();
or maybe this...
var menus = (from m in _context.Menus
join ms in _context.MenuSections on m.MenuId equals ms.MenuId
select new {m, ms.Order})
.OrderBy(x => x.Order)
.Select(x => x.m)
.Distinct();
In that second case, you're projecting the sort column into a new type, sorting on it, then selecting just the original object, and distincting on that.
Just an FYI, I did manage to make this work by sorting as I performed the output.
My original intention was to have a presorted data set to work with.
Here is an example of what I meant:
var menus = from m in _context.Menus select m;
foreach (var menu in menus)
{
Console.WriteLine(menu.Name);
foreach (var menuSection in menu.MenuSections.OrderBy(o => o.Order))
{
Console.WriteLine("\t" + menuSection.Name + ", " + menuSection.Order);
}
}
Related
I have 2 queries that work, I was hoping to combine them to reduce the database calls.
var locations = from l in db.Locations
where l.LocationID.Equals(TagID)
select l;
I do the above because I need l.Name, but is there a way to take the above results and put them into the query below?
articles = from a in db.Articles
where
(
from l in a.Locations
where l.LocationID.Equals(TagID)
select l
).Any()
select a;
Will I actually be reducing any database calls here?
This seems a bit complicated because Locations appears to be a multi-value property of Articles and you want to only load the correct one. According to this answer to a similar question you need to use a select to return them separately in one go so e.g.
var articles = from a in db.Articles
select new {
Article = a,
Location = a.Locations.Where(l => l.LocationId == TagId)
};
First failed attempt using join:
var articlesAndLocations = from a in db.Articles
join l in a.Locations
on l.LocationID equals TagID
select new { Article = a, Location = l };
(I usually use the other LINQ syntax though so apologies if I've done something stupid there.)
Could you not use the Include() method here to pull in the locations which are associated with each article, then select both the article and location object? or the properties you need from each.
The include method will ensure that you don't need to dip into the db twice, but will allow you to access properties on related entities.
You would need to use a contains method on an IEnumerable I believe, something like this:
var tagIdList = new List() { TagID };
var articles = from a in db.Articles.Include("Locations")
where tagIdList.Contains(from l in a.Locations select l.LocationID)
select new { a, a.Locations.Name };
(Untested)
So I have a list(table) of about 100k items and I want to retrieve all values that match a given list.
I have something like this.
the Table Sections key is NOT a primary key, so I'm expecting each value in listOfKeys to return a few rows.
List<int> listOfKeys = new List<int>(){1,3,44};
var allSections = Sections.Where(s => listOfKeys.Contains(s.id));
I don't know if it makes a difference but generally listOfKeys will only have between 1 to 3 items.
I'm using the Entity Framework.
So my question is, is this the best / fastest way to include a list in a linq expression?
I'm assuming that it isn't better to use another .NETICollection data object. Should I be using a Union or something?
Thanks
Suppose the listOfKeys will contain only small about of items and it's local list (not from database), like <50, then it's OK. The query generated will be basically WHERE id in (...) or WHERE id = ... OR id = ... ... and that's OK for database engine to handle it.
A Join would probably be more efficient:
var allSections =
from s in Sections
join k in listOfKeys on s.id equals k
select s;
Or, if you prefer the extension method syntax:
var allSections = Sections.Join(listOfKeys, s => s.id, k => k, (s, k) => s);
from item in db.Items
join ci in db.ChainStoreItems on item.ItemId equals ci.ItemId
where ci.ChainStoreId == 2
select item
The problem is as follows: Item has a set of ChainStoreItems. I want to write a query which returns an Item which doesn't have a set of ChainStoreItems it should hold only the one specific ChainStoreItem for the selected ChainStore.
So I only want do have the additional columns in item which came from ChainStoreItem however this is possible
That's a SQL statement which would do what I want
SELECT
ChainStoreItems.ChainStoreId, ChainStoreItems.ItemId,
Item.ProcStatus, Item.Del, Item.LastUpdate,
ChainStoreItems.AllowToReturn,
ChainStoreItems.AllowToSale
FROM
ChainStoreItems
INNER JOIN
Item ON ChainStoreItems.ItemId = Item.ItemId
WHERE
(ChainStoreItems.ChainStoreId = 140)
Is this what you are getting at!?
var result = from item in db.Items
join ci in db.ChainStoreItems
on item.ItemId equals ci.ItemId
where ci.ChainStoreId == 2
into itemci // note grouping
select new
{
//Whatever you want in here
};
return result;
Sorry i'm still not quite seeing what exactly it is you want to achieve. As far as i'm aware it's simply a matter of creating a join and pulling back the appropriate details
Does ChainStoreItem have an Item property?
In which case, is it just:
from csi in ChainStoreItems
where csi.ChainStoreId == 140
select new { ChainStoreItem = csi, Item = csi.Item }
... or have I misunderstood?
I have the following expression in linq (its a join) and i am selecting into "J" because i need to use J later (currently i just selecting J but once i have this fixed i plan on use J within another subquery after)
But it won't let me supply a where using the "V" side hence v.IdOFfice is invalid.
I have tried swapping around the joins and that what happens i can't use the "GVT"..
WIth specifying the where it works perfect but i need to specify 2 wheres that are present in the 2 tables ... hence IdOffice and IdTariff are in there own tables .. they are not both ....
(from gvt in Tariffs
join v in Items
on gvt.IdGroupItem equals v.IdGroupItem
into j
where v.IdOffice == 1 && gvt.IdTariff == 111
select j).Take(50)
Probably something silly, it appears the table specified after the join i am not able to use in the where?
Any ideas?
Thanks
This is basically what i am trying to achieve
from gvt in Tariffs
join v in Items
on gvt.IdGroupItem equals v.IdGroupItem
into j
where v.IdOffice == 1 && gvt.IdTariff == 111
select new
{
id = v.IdItem
Tariff = from j
{
test = j.TariffDesc,
test1 = j.TariffPrice
}
basicaly i end up with 1 record with Id and a field which as many tariffs inside - if this makes sense?
}
Query working great,
it would be nice to be able to use an extension method (c#) like so ... is this possible so i can dynamically set tariff ... so for example i do the query and i have an extension method (which i already use on simple queries) like so
public static IQueryable<Models.ItemTariffCol> WithTariffId(this IQueryable<Models.ItemTariffCol> qry, int tariffId)
{
return from t in qry
where t.IdTarifa == tariffId
select t;
}
this makes it very extensible ? If its a normal where i can do this but the query isn't in the where
Thank you.
You're doing a group join here, since you're using into. This means that for every gvt, you have not one Item, but possibly several (or none). The list of all items is stored in j, as an IEnumerable<Item>. If you want to select all tariffs for which there's at least one item with IdOffice == 1, then you can do it like this:
from gvt in Tariffs
join v in Items
on gvt.IdGroupItem equals v.IdGroupItem
into j
where gvt.IdTariff == 111 && j.Any(v => v.IdOffice == 1)
...
After the answer edit, it seems that you've started from the wrong direction as well - so far as I can see, you want a list of tariffs for every item, not the list of items for every tariff. For that, you need to reverse your join:
from item in Items
join tariff in Tariffs
on item.IdGroupItem equals tariff.IdGroupItem
into tariffs
where item.IdOffice == 1
select new
{
Id = item.IdItem,
Tariffs = from tariff in tariffs
where tariff.IdTariff == 111
select new { tariff.TariffDesc, tariff.TariffPrice }
}
Or you could filter tariffs right in the join:
from item in Items
join tariff in (from t in Tariffs where t.IdTariff == 111 select t)
on item.IdGroupItem equals tariff.IdGroupItem
into tariffs
where item.IdOffice == 1
select new
{
Id = item.IdItem,
Tariffs = from tariff in tariffs
select new { tariff.TariffDesc, tariff.TariffPrice }
}
I have some Linq code and it's working fine. It's a query that has a subquery in the Where clause. This subquery is doing a groupby. Works great.
The problem is that I don't know how to grab one of the results from the subquery out of the subquery into the parent.
Frst, here's the code. After that, I'll expplain what piece of data i'm wanting to extract.
var results = (from a in db.tblProducts
where (from r in db.tblReviews
where r.IdUserModified == 1
group r by
new
{
r.tblAddress.IdProductCode_Alpha,
r.tblAddress.IdProductCode_Beta,
r.tblAddress.IdProductCode_Gamma
}
into productGroup
orderby productGroup.Count() descending
select
new
{
productGroup.Key.IdProductCode_Alpha,
productGroup.Key.IdProductCode_Beta,
productGroup.Key.IdProductCode_Gamma,
ReviewCount = productGroup.Count()
}).Take(3)
.Any(
r =>
r.IdProductCode_Alpha== a.IdProductCode_Alpha&&
r.IdProductCode_Beta== a.IdProductCode_Beta&&
r.IdProductCode_Gamma== a.IdProductCode_Gamma)
where a.ProductFirstName == ""
select new {a.IdProduct, a.FullName}).ToList();
Ok. I've changed some field and tables names to protect the innocent. :)
See this last line :-
select new {a.IdProduct, a.FullName}).ToList();
I wish to include in that the ReviewCount (from the subquery). I'm jus not sure how.
To help understand the problem, this is what the data looks like.
Sub Query
IdProductCode_Alpha = 1, IdProductCode_Beta = 2, IdProductCode_Gamma = 3, ReviewCount = 10
... row 2 ...
... row 3 ...
Parent Query
IdProduct = 69, FullName = 'Jon Skeet's Wonder Balm'
So the subquery grabs the actual data i need. The parent query determines the correct product, based on the subquery filters.
EDIT 1: Schema
tblProducts
IdProductCode
FullName
ProductFirstName
tblReviews (each product has zero to many reviews)
IdProduct
IdProductCode_Alpha (can be null)
IdProductCode_Beta (can be null)
IdProductCode_Gamma (can be null)
IdPerson
So i'm trying to find the top 3 products a person has done reviews on.
The linq works perfectly... except i just don't know how to include the COUNT in the parent query (ie. pull that result from the subquery).
Cheers :)
Got it myself. Take note of the double from at the start of the query, then the Any() being replaced by a Where() clause.
var results = (from a in db.tblProducts
from g in (
from r in db.tblReviews
where r.IdUserModified == 1
group r by
new
{
r.tblAddress.IdProductCode_Alpha,
r.tblAddress.IdProductCode_Beta,
r.tblAddress.IdProductCode_Gamma
}
into productGroup
orderby productGroup.Count() descending
select
new
{
productGroup.Key.IdProductCode_Alpha,
productGroup.Key.IdProductCode_Beta,
productGroup.Key.IdProductCode_Gamma,
ReviewCount = productGroup.Count()
})
.Take(3)
Where(g.IdProductCode_Alpha== a.IdProductCode_Alpha&&
g.IdProductCode_Beta== a.IdProductCode_Beta&&
g.IdProductCode_Gamma== a.IdProductCode_Gamma)
where a.ProductFirstName == ""
select new {a.IdProduct, a.FullName, g.ReviewCount}).ToList();
While I don't understand LINQ completely, but wouldn't the JOIN work?
I know my answer doesn't help but it looks like you need a JOIN with the inner table(?).
I agree with shahkalpesh, both about the schema and the join.
You should be able to refactor...
r => r.IdProductCode_Alpha == a.IdProductCode_Alpha &&
r.IdProductCode_Beta == a.IdProductCode_Beta &&
r.IdProductCode_Gamma == a.IdProductCode_Gamma
into an inner join with tblProducts.