C#从每个地区选择前2名产品详细信息

从给定的产品列表中

List<Product> productList = new List<Product>();
productList.Add(new Product("P001", 34566.78M, "North"));
productList.Add(new Product("P004", 4566.78M, "East"));
productList.Add(new Product("P007", 14566.78M, "South"));

productList.Add(new Product("P010", 2456.178M, "South"));
productList.Add(new Product("P011", 341566.78M, "North"));
productList.Add(new Product("P006", 64566.878M, "East"));

productList.Add(new Product("P00188", 664566.78M, "East"));
productList.Add(new Product("P00111", 3444566.78M, "North"));
productList.Add(new Product("P00134", 3234566.78M, "South"));

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首先按区域分组，然后在每个组中执行OrderBy/Take。例如：

var query = productList
   .GroupBy(r => r.Region)
   .Select(group => new { Region = group.Key,
                          Orders = group.OrderByDescending(p => p.ProductPrice)
                                        .Take(2) });

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它不漂亮，可读性也不太好，但如果你必须用一句话来表达，这会帮你解决问题

var q = productList.Select(pl => pl.Region)
                .Distinct()
                .ToList()
                .SelectMany(region => productList.Where(pl => pl.Region == region)
                                                 .OrderByDescending(pl => pl.ProductPrice)
                                                 .Take(2));

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不过，我建议将其拆分以便于阅读。

乔恩·斯基特总是在那里等待救援！：）

var q = productList.Select(pl => pl.Region)
                .Distinct()
                .ToList()
                .SelectMany(region => productList.Where(pl => pl.Region == region)
                                                 .OrderByDescending(pl => pl.ProductPrice)
                                                 .Take(2));