pagination in asp.net mvc

Question

I have categories and subcategories. Each subcategory has some products. e.g programming category has | C# , java , basic subcategories | where c# has c# 3 , c# 3.5 products | java has java ee , java me and so on

I want to select 10 products from categories using linq to EF.

The problem is that I don't want to load all products from the database and then sort them and then select 10 of them.

I want a solution which i can just take 10 products from database without transferring all products from the database back to web server.

I know that EF is greedy and would take only 10 products and skip some. but in my case which i have categories and subcategories so I think I should first select all products from different subcategories belonging to a category and append them to a list which cause bringing all products to server and then select 10 of them.

What is the best practice so that i don't have to transfer all products to server?

you could use something like github.com/TroyGoode/PagedList to do the paging etc for you btw — Manatherin
– Manatherin, Commented Apr 22, 2012 at 10:40

Mahmoud Gamal · Accepted Answer · 2012-04-22 09:28:07Z

2

You can do this in one query:

var pagedProducts = _db.Categories.Join( 
    _db.Products,
    c => c.CategoryId,
    p => p.CategoryId,
    (Category, Products) =>
       new
       {
           CategoryType = Category,
           ItsProducts  = Products
       })
        .OrderBy(g => g.Category.Name)
        .Skip((CurrentPage - 1) * pageSize)
        .Take(pageSize);

edited Apr 22, 2012 at 9:28

answered Apr 22, 2012 at 8:19

Mahmoud Gamal

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3 Comments

Amir Jalali Over a year ago

what about sorting? shouldn't it get sorted first and then paginated? how to sort it?

Mahmoud Gamal Over a year ago

@cSharpper, You should OrderBy before Take and Skip to make the pagination get the page correctly, or at least keep the default order.

Amir Jalali Over a year ago

your code is correct but i finally wrote this code : var categoryModel = storeDB.Categories.Single(c => c.CategoryId == categoryId); var subCategoriesModel = storeDB.SubCategories.Where(c => c.CategoryId == categoryModel.CategoryId); var subcategoriesID = subCategoriesModel.Select(s => s.SubCategoryId).ToList(); var products = (from p in storeDB.Products where subcategoriesID.Contains(p.SubCategoryId) select p).OrderBy(p => p.ProductId).Skip((page - 1) * pageSize).Take(pageSize);

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