[英]How to get distinct with highest value using Linq
假設我有以下數據:
Name Priority
A 3
A 5
B 1
C 1
C 3
C 2
我想獲得具有最高優先級的不同名稱列表,因此結果如下所示:
Name Priority
A 5
B 1
C 3
我如何使用Linq來做到這一點?
var query = yourData
.GroupBy(x => x.Name,
(k, g) => g.Aggregate((a, x) => (x.Priority > a.Priority) ? x : a));
// and a quick test...
foreach (var result in query)
{
Console.WriteLine(result.Name + " " + result.Priority);
}
這是另一種方法 :
var items = new List<Tuple<string, int>>()
{
Tuple.Create("A", 3),
Tuple.Create("A", 5),
Tuple.Create("B", 1),
Tuple.Create("C", 1),
Tuple.Create("C", 3),
Tuple.Create("C", 2)
};
var results = items.GroupBy(i => i.Item1)
.SelectMany(g => g
.Where(i => i.Item2 == g.Max(m => m.Item2)))
.Distinct();
或者,如果您更喜歡使用C#LINQ語法:
results = (from item in items
group item by item.Item1 into groupedItems
let maxPriority = groupedItems.Max(item => item.Item2)
from element in groupedItems
where element.Item2 == maxPriority
select element).Distinct();
另一種沒有聚合的簡單方法
var listNP = new List<NP>()
{
new NP() {name="A",priority=3},
new NP() {name="A",priority=5},
new NP() {name="b",priority=1},
new NP() {name="b",priority=1},
new NP() {name="c",priority=3},
new NP() {name="c",priority=2},
};
var np = listNP.GroupBy(x => x.name).Select(y => new
{
name = y.Key,
max = y.Max(x=>x.priority)
}).ToList();
更新:
var np = listNP.GroupBy(x => x.name)
.Select(y => y.OrderByDescending(z => z.priority).First()).ToList();
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