使用lambda / linq查詢返回組中的最小值

Question

我需要幫助創建一個lambda表達式來查詢以下列表，以便檢索每個通道中價格最低的項目。 即，對於該示例項目A，D和G.

class Radio
{
    public string Name { get; set; }
    public int Channel { get; set; }
    public decimal Price { get; set; }
}

List<Radio> radios = new List<Radio>();
radios.Add(new Radio() { Name = "A", Channel = 1, Price = 10 });
radios.Add(new Radio() { Name = "B", Channel = 1, Price = 20 });
radios.Add(new Radio() { Name = "C", Channel = 1, Price = 30 });
radios.Add(new Radio() { Name = "D", Channel = 2, Price = 10 });
radios.Add(new Radio() { Name = "E", Channel = 2, Price = 20 });
radios.Add(new Radio() { Name = "F", Channel = 2, Price = 30 });
radios.Add(new Radio() { Name = "G", Channel = 3, Price = 10 });
radios.Add(new Radio() { Name = "H", Channel = 3, Price = 20 });
radios.Add(new Radio() { Name = "I", Channel = 3, Price = 30 });

Answer 1

使用Linq，

第一組使用Enumerable.GroupBy
然后使用Enumerable.OrderBy進行排序
然后采取首先在組中的每個分類項

    radios.GroupBy(x=> x.Channel).Select(x=>x.OrderBy(y=>y.Price)).Select(x=>x.First());

Answer 2

您也可以在不對每個組進行昂貴的排序的情況下執行此操作：

radios.GroupBy(x => x.Channel).Select(g =>
    g.Aggregate((r1, r2) => r1.Price < r2.Price ? r1 : r2));

Aggregate遍歷每個組一次，跟蹤到目前為止發現的最便宜的無線電，如果找到更便宜的無線電，則替換它。