C#LINQ:获取最高价格的商品

Question

我有一个我的对象列表:

class MyObj
{
    public String Title { get; set; }
    public Decimal Price { get; set; }
    public String OtherData { get; set; }
}

var list = new List<MyObj> {
 new MyObj { Title = "AAA", Price = 20, OtherData = "Z1" },
 new MyObj { Title = "BBB", Price = 20, OtherData = "Z2" },
 new MyObj { Title = "AAA", Price = 30, OtherData = "Z5" },
 new MyObj { Title = "BBB", Price = 10, OtherData = "Z10" },
 new MyObj { Title = "CCC", Price = 99, OtherData = "ZZ" }
};

获得具有唯一Title和MAX(价格)的列表的最佳方法是什么.结果列表需要是:

var ret = new List<MyObj> {
 new MyObj { Title = "BBB", Price = 20, OtherData = "Z2" },
 new MyObj { Title = "AAA", Price = 30, OtherData = "Z5" },
 new MyObj { Title = "CCC", Price = 99, OtherData = "ZZ" }
};

Answer 1

好吧,你可以这样做:

var query = list.GroupBy(x => x.Title)
                .Select(group =>
                {
                    decimal maxPrice = group.Max(x => x.Price);
                    return group.Where(x => x.Price == maxPrice)
                                .First();
                };

如果你需要LINQ to SQL(你不能使用语句lambdas),你可以使用:

var query = list.GroupBy(x => x.Title)
       .Select(group => group.Where(x => x.Price == group.Max(y => y.Price))
                             .First());

请注意,在每次迭代中效率较低的LINQ to Objects中Where,它会重新计算最大价格.

.First()如果您希望能够返回具有给定名称的多个项目(如果它们具有相同的价格),则调整该部分.

在LINQ to Objects中你也可以使用MoreLINQ的MaxBy方法:

var query = list.GroupBy(x => x.Title)
                .Select(group => group.MaxBy(x => x.Price));