Question

我是LINQ的新手，并尝试使用MVC和LINQ构建一个网站。我想展示视图最多的前5个产品。我有2个表，如下所示，我解释尽可能简单。

PRODUCT
-------
ID
NAME

PRODUCT_VIEWS_TABLE
-------
ID
PRODUCT_ID

每次查看产品时，我都会向PRODUCT_VIEWS_TABLE插入一个新行。如何为此编写LINQ查询？

(from c in db.PRODUCT select c).Take(5)

Answer 1

这个怎么样：

var top5 = productViews
             .GroupBy(view => view.ProductId)   // group views by product
             .OrderByDescending(g => g.Count()) // order from most- to least-viewed
             .Take(5)                           // take the top 5
             .Select(g => g.First().Product);   // fetch the corresponding product

Answer 2

var topProductsIds = db.PRODUCT_VIEWS_TABLE // table with a row for each view of a product
    .GroupBy(x => x.PRODUCT_ID) //group all rows with same product id together
    .OrderByDescending(g => g.Count()) // move products with highest views to the top
    .Take(5) // take top 5
    .Select(x => x.Key) // get id of products
    .ToList(); // execute query and convert it to a list

var topProducts = db.PRODUCTS // table with products information
    .Where(x=> topProductsIds.Contains(x.ID)); // get info of products that their Ids are retrieved in previous query

Answer 3

试试这个：

var topProducts = m_context.PRODUCTS
    .Join(m_context.PRODUCT_VIEW, product=> product.Id, view => view.ProductId,
        (product, view ) => new { ProductId = product.Id, ViewId = view.Id})
    .GroupBy(g => g.ProductId)
    .Select(s => new {
        Id = s.Key,
        ViewCount= s.Count()
    })
    .OrderByDescending(o => o.ViewCount)
    .Take(5).ToList();

如何获得最高视图的前5名产品？

3 个答案: