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How can I get the best seller by product group using LINQ

I need to retrieve the name, product type and sum of the seller with the highest sales in each product type using linq and return the list to a view.
{
public ActionResult Query2()
{
// this part gets me everything into one model type
List<QueryViewModel> result = db.SaleProducts
.GroupBy(prod => prod.Type)
.SelectMany(sale => sale.Select(
row => new QueryViewModel
{
Seller = row.Sale.User.Name,
ProductType = row.Type,
Sales = (double)sale.Where(x => x.Sale.UserId == row.Sale.UserId && x.Type.Equals(row.Type)).Sum(price => price.Price)
}
)).Distinct().ToList<QueryViewModel>();
// this gives me the best per product type but i cant get the seller name
List<QueryViewModel> filter = (from res in result
group res by res.ProductType into prodGroup
select new QueryViewModel
{
ProductType = prodGroup.Key,
Sales = prodGroup.Max(x => x.Sales)
}).ToList<QueryViewModel>();
// this is really just to get the seller name at this point
List<QueryViewModel> something = (from res in result
join f in filter on res.Sales equals f.Sales
select new QueryViewModel
{
Seller = res.Seller,
ProductType = res.ProductType,
Sales = res.Sales
}).ToList<QueryViewModel>();
return View(something);
}
}
It should return a list of QueryViewModel(name, product type, total sales).
It does return that, but this seems horribly messy and I'm not understanding LINQ enough to clear this up.
Is there a better cleaner way to achieve my desired output?

The first grouping should be by type and Seller.
Something like this should get you going:
Quote_Masters.GroupBy(qm => new { qm.OrderTypeId, qm.SalesRepEmployeeId })
.Select(x => new { Name = x.Key.SalesRepEmployeeId, x.Key.OrderTypeId, Total = x.Sum(qm => qm.Total_Price) })
.OrderByDescending(x => x.Total).GroupBy(x => x.OrderTypeId).Select(x => x.FirstOrDefault())
Just change out your appropriate tables and fields.
Edit: Your select to QueryViewModel would be the new {Name = x.Key.SalesRepEmployeeId, x.Key.OrderTypeId, Total = x.Sum(qm => qm.Total_Price)}

Select by ID from a list

I have a table of products and a table of categories, I can select by the ID of the Category like this:
var result = db.tblProducts.Where(p => p.tblCategories.Any(c => c.ID == 1));
However, I want to be able to select based on a list of Categories:
var catIDs = new List<int>() { 1,2,3 };
var results = db.tblProducts.Where(r => r.tblCategories.Any(t => catIDs.Contains(t.ID)));
I get the following error:
LINQ to Entities does not recognize the method 'Boolean Contains(Int32)' method, and this method cannot be translated into a store expression.
Presumably because I am using Contains to compare entities to local variables. Is there a way to do this?

Try create Expression from values. F.e.:
static Expression MakeOrExpression<T, P>(Expression<Func<T, P>> whatToCompare, IEnumerable<P> values)
{
Expression result = Expression.Constant(true);
foreach (var value in values)
{
var comparison = Expression.Equal(whatToCompare, Expression.Constant(value));
result = Expression.Or(result, comparison);
}
return result;
}
How to use:
var results = db.tblProducts.Where(r => r.tblCategories.Any(MakeOrExpression(t => t.ID, catIDs)));
The method MakeOrExpression will create an expression t.ID == 1 || t.ID == 2 || t.ID == 3 for list { 1, 2, 3 } dynamically, and then EF will translate it to SQL condition.

Maybe you can use this:
var catIDs = new List<int>() { 1,2,3 };
var results = db.tblCategories
.Where(t => catIDs.Contains(t.ID))
.SelectMany(t => t.tblProducts)
.Distinct();

Try this:
var query=from p in db.tblProducts
from c in p.tblCategories
where catIDs.Contains(c.ID)
select p;
If at least one of the categories of the product is in the catIDs list, then the product will be seleted.
Another option could be start by the categories (I'm guessing you have a many to many relationship between Product and Category and you have a collections of products in your Category entity):
var query=db.tblCategories.Where(c => catIDs.Contains(c.ID)).SelectMany(c=>c.tblProducts).Distinct();

Try this code :
var catIDs = new List<int>() { 1,2,3 };
var results = db.tblProducts.Where(r => catIDs.Any(c => c == r.tblCategories.Id));

Using the results linq query in another linq query

Good day!
Tell me whether it is possible to use the result of a Linq query in another Linq query?
For example:
List<Member> memberList = db.Members.Where(m=>m.Year == 20013).ToList();
var result = (from members in memberList
from documents in Archive.Where(d=>d.MemberId = members.Id).DefaultIfEmpty()
select new ArchiveRecord
{
member = members,
documentId = documentsId
}).ToList();
At the same time the implementation of the second request falls with the error (There is already an open DataReader associated with this Command which must be closed first).
Please tell me where I made mistakes.
Thank you!

I don't know how to make nested linq query but i have solution for you.
Try this:
List<Member> memberList = db.Members.Where(m => m.Year == 20013).ToList();
var membersIds = memberList.Select(m => m.Id);
var result = (from documents in Archive.Where(d => membersIds.Contains(d.MemberId)).DefultIfEmpty()
select new ArchiveRecord
{
member = members,
documentId = documentsId
}).ToList();

Enable Multiple Active Result Sets ("MultipleActiveResultSets=True") in your connection string:
https://msdn.microsoft.com/en-us/library/h32h3abf(v=vs.110).aspx

I believe this should work (Single query):
var memberList = db.Members.Where(m=>m.Year == 20013);
var result = (from members in memberList
from documents in Archive.Where(d=>d.MemberId = members.Id).DefaultIfEmpty()
select new ArchiveRecord
{
member = members,
documentId = documentsId
}).ToList();
This definitely should work (Single query):
var result = (from members in db.Members
from documents in Archive.Where(d=>d.MemberId = members.Id).DefaultIfEmpty()
where members.year == 20013
select new ArchiveRecord
{
member = members,
documentId = documentsId
}).ToList();
and this (Two queries):
var membersIds = db.Members
.Where(m => m.Year == 20013)
.Select(m => m.Id)
.ToList();
var result = (from documents in Archive.Where(d => membersIds.Contains(d.MemberId)).DefultIfEmpty()
select new ArchiveRecord
{
member = members,
documentId = documentsId
}).ToList();
and this assuming you have created a navigation property on members to archive, and it is a 1-many relationship (Single query):
var result=db.Archives
.Where(a=>a.Member.Year==20013)
.Select(a=> new ArchiveRecord {
member=a.Member,
documentId=a.documentsId
}).ToList();

Group By Query with Entity Framework

In my application I have Movements associated with a category.
I want a list of the most frequent category.
My objects are:
Category: catId, catName
Movement: Movid, movDate, movMount, catId
I think it would have to raise it with a "Group By" query (grouping by catId and getting those more)
(Im using Entity Framework 6 in c#)
From already thank you very much!

IMPORTANT: Entity Framework 7 (now renamed to Entity Framework Core 1.0) does not yet support GroupBy() for translation to GROUP BY in generated SQL. Any grouping logic will run on the client side, which could cause a lot of data to be loaded.
https://blogs.msdn.microsoft.com/dotnet/2016/05/16/announcing-entity-framework-core-rc2

group the movements by category and select catid and count.
join this result with category to get the name and then descending sort the results on count.
var groupedCategories = context.Movements.GroupBy(m=>m.catId).Select(g=>new {CatId = g.Key, Count = g.Count()});
var frequentCategories = groupedCategories.Join(context.Categories, g => g.CatId, c => c.catId, (g,c) => new { catId = c.catId, catName = c.catName, count = g.Count }).OrderByDescending(r => r.Count);
foreach (var category in frequentCategories)
{
// category.catId, category.catName and category.Count
}

i hope this help:
var query = dbContext.Category.Select(u => new
{
Cat = u,
MovementCount = u.Movement.Count()
})
.ToList()
.OrderByDescending(u => u.MovementCount)
.Select(u => u.Cat)
.ToList();

I resolved the problem!
I used the proposal by "Raja" solution (Thanks a lot!).
This return a collection composed of "Category" and "Count". I Change it a bit to return a list of Categories.
var groupedCategories = model.Movement.GroupBy(m => m.catId).Select(
g => new {catId= g.Key, Count = g.Count() });
var freqCategories= groupedCategories.Join(model.Category,
g => g.catId,
c => c.catId,
(g, c) => new {category = c, count = g.Count}).OrderByDescending(ca => ca.count).Select(fc => fc.category).ToList ();

you just need to use navigation property on category simply, you have a navigation property on category contains all related Movement, i call it Movements in following query. you can write your query like this, with minimum of connection with DB.
class Cat
{
public Guid catId { get; set; }
public string catName { get; set; }
public IEnumerable<Movement> Movements { get; set; }
public int MovementsCount { get { return Movements.Count(); } }
}
var Categories = category.Select(u => new Cat()
{
u.catId,
u.catName,
Movements = u.Movements.AsEnumerable()
}).ToList();
var CategoriesIncludeCount = Categories.OrderBy(u => u.MovementsCount).ToList();

How to perform Join between multiple tables in LINQ lambda

I am trying to perform a Join between multiple tables in LINQ. I have the following classes:
Product {Id, ProdName, ProdQty}
Category {Id, CatName}
ProductCategory{ProdId, CatId} //association table
And I use the following code (where product, category and productcategory are instances of the above classes):
var query = product.Join(productcategory, p => p.Id, pc => pc.ProdID, (p, pc) => new {product = p, productcategory = pc})
.Join(category, ppc => ppc.productcategory.CatId, c => c.Id, (ppc, c) => new { productproductcategory = ppc, category = c});
With this code I obtain an object from the following class:
QueryClass { productproductcategory, category}
Where producproductcategory is of type:
ProductProductCategoryClass {product, productcategory}
I do not understand where the joined "table" is, I was expecting a single class that contains all the properties from the involved classes.
My aim is to populate another object with some properties resulting from the query:
CategorizedProducts catProducts = query.Select(m => new { m.ProdId = ???, m.CatId = ???, //other assignments });
how can I achieve this goal?

For joins, I strongly prefer query-syntax for all the details that are happily hidden (not the least of which are the transparent identifiers involved with the intermediate projections along the way that are apparent in the dot-syntax equivalent). However, you asked regarding Lambdas which I think you have everything you need - you just need to put it all together.
var categorizedProducts = product
.Join(productcategory, p => p.Id, pc => pc.ProdId, (p, pc) => new { p, pc })
.Join(category, ppc => ppc.pc.CatId, c => c.Id, (ppc, c) => new { ppc, c })
.Select(m => new {
ProdId = m.ppc.p.Id, // or m.ppc.pc.ProdId
CatId = m.c.CatId
// other assignments
});
If you need to, you can save the join into a local variable and reuse it later, however lacking other details to the contrary, I see no reason to introduce the local variable.
Also, you could throw the Select into the last lambda of the second Join (again, provided there are no other operations that depend on the join results) which would give:
var categorizedProducts = product
.Join(productcategory, p => p.Id, pc => pc.ProdId, (p, pc) => new { p, pc })
.Join(category, ppc => ppc.pc.CatId, c => c.Id, (ppc, c) => new {
ProdId = ppc.p.Id, // or ppc.pc.ProdId
CatId = c.CatId
// other assignments
});
...and making a last attempt to sell you on query syntax, this would look like this:
var categorizedProducts =
from p in product
join pc in productcategory on p.Id equals pc.ProdId
join c in category on pc.CatId equals c.Id
select new {
ProdId = p.Id, // or pc.ProdId
CatId = c.CatId
// other assignments
};
Your hands may be tied on whether query-syntax is available. I know some shops have such mandates - often based on the notion that query-syntax is somewhat more limited than dot-syntax. There are other reasons, like "why should I learn a second syntax if I can do everything and more in dot-syntax?" As this last part shows - there are details that query-syntax hides that can make it well worth embracing with the improvement to readability it brings: all those intermediate projections and identifiers you have to cook-up are happily not front-and-center-stage in the query-syntax version - they are background fluff. Off my soap-box now - anyhow, thanks for the question. :)

What you've seen is what you get - and it's exactly what you asked for, here:
(ppc, c) => new { productproductcategory = ppc, category = c}
That's a lambda expression returning an anonymous type with those two properties.
In your CategorizedProducts, you just need to go via those properties:
CategorizedProducts catProducts = query.Select(
m => new {
ProdId = m.productproductcategory.product.Id,
CatId = m.category.CatId,
// other assignments
});

take look at this sample code from my project
public static IList<Letter> GetDepartmentLettersLinq(int departmentId)
{
IEnumerable<Letter> allDepartmentLetters =
from allLetter in LetterService.GetAllLetters()
join allUser in UserService.GetAllUsers() on allLetter.EmployeeID equals allUser.ID into usersGroup
from user in usersGroup.DefaultIfEmpty()// here is the tricky part
join allDepartment in DepartmentService.GetAllDepartments() on user.DepartmentID equals allDepartment.ID
where allDepartment.ID == departmentId
select allLetter;
return allDepartmentLetters.ToArray();
}
in this code I joined 3 tables and I spited join condition from where clause
note: the Services classes are just warped(encapsulate) the database operations

public ActionResult Index()
{
List<CustomerOrder_Result> obj = new List<CustomerOrder_Result>();
var orderlist = (from a in db.OrderMasters
join b in db.Customers on a.CustomerId equals b.Id
join c in db.CustomerAddresses on b.Id equals c.CustomerId
where a.Status == "Pending"
select new
{
Customername = b.Customername,
Phone = b.Phone,
OrderId = a.OrderId,
OrderDate = a.OrderDate,
NoOfItems = a.NoOfItems,
Order_amt = a.Order_amt,
dis_amt = a.Dis_amt,
net_amt = a.Net_amt,
status=a.Status,
address = c.address,
City = c.City,
State = c.State,
Pin = c.Pin
}) ;
foreach (var item in orderlist)
{
CustomerOrder_Result clr = new CustomerOrder_Result();
clr.Customername=item.Customername;
clr.Phone = item.Phone;
clr.OrderId = item.OrderId;
clr.OrderDate = item.OrderDate;
clr.NoOfItems = item.NoOfItems;
clr.Order_amt = item.Order_amt;
clr.net_amt = item.net_amt;
clr.address = item.address;
clr.City = item.City;
clr.State = item.State;
clr.Pin = item.Pin;
clr.status = item.status;
obj.Add(clr);
}

var query = from a in d.tbl_Usuarios
from b in d.tblComidaPreferidas
from c in d.tblLugarNacimientoes
select new
{
_nombre = a.Nombre,
_comida = b.ComidaPreferida,
_lNacimiento = c.Ciudad
};
foreach (var i in query)
{
Console.WriteLine($"{i._nombre } le gusta {i._comida} y nació en {i._lNacimiento}");
}

it has been a while but my answer may help someone:
if you already defined the relation properly you can use this:
var res = query.Products.Select(m => new
{
productID = product.Id,
categoryID = m.ProductCategory.Select(s => s.Category.ID).ToList(),
}).ToList();