Question

我有一个标准的商店架构，其中包含一个包含Products的InvoiceLine表。我希望按销售额列出销售前5名的产品。最干净的方法是什么？这不是最好的方法：

    private List<Product> GetTopProducts(int count)
    {
        var topProducts = from invoiceLine in storeDB.InvoiceLines
                        group invoiceLine by invoiceLine.ProductId into grouping
                        orderby grouping.Count() descending
                        select new 
                        {
                            Products = from Product in storeDB.Products 
                            where grouping.Key == Product.ProductId
                            select Product
                        };
        return topProducts.AsEnumerable().Cast<Product>().Take(count).ToList<Product>();
    }

Answer 1

我无法准确测试这个，但您可以简单地对生成的“Product”属性进行分组吗？

return (from i in storeDB.InvoiceLines
                   group i by i.Product into g
                   orderby g.Count() descending
                   select g.Key)
    .Take(count).ToList();

Answer 2

Cleaner仍在设计器中添加Product和InvoiceLine之间的关系 - 创建Product.InvoiceLines属性。

List<Product> result = storeDB.Products
  .OrderByDescending(p => p.InvoiceLines.Count())
  .Take(count)
  .ToList();

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