List <int>使用linq過濾

Question

我有一個List對象，它包含Id值，例如它包含： 1,2,10,1,23,11,1,4,2,2，..等我需要找到在C＃中使用Linq發生了多少次「1」，「2」等...發生了 。

請幫忙。

Answer 1

這是非常簡單的使用Enumerable.GroupBy：

var grouped = list.GroupBy(x => x); 

foreach (var group in grouped) 
{ 
    Console.WriteLine("{0} appears {1} times", group.Key, group.Count()); 
} 

或者：

var query = list.GroupBy(x => x, (x, g) => new { Key = x, Count = g.Count() })); 

foreach (var result in query) 
{ 
    Console.WriteLine("{0} appears {1} times", result.Key, result.Count); 
} 

（所不同的是隻是，當我們轉換成組的結果，真的。）

Answer 2

使用GroupBy：

var les = new[] { 1, 2, 10, 1, 23, 11, 1, 4, 2, 2 }; 

var result = les 
    .GroupBy(i => i, (e, g) => new { Value = e, Count = g.Count() }); 

或者用替代語法：

var result = 
    from i in les 
    group i by i 
    into g 
    select new { Value = g.Key, Count = g.Count() }; 

Answer 3

var l = new List<int> {1,2,10,1,23,11,1,4,2,2}; 
l.GroupBy(i => i) 
    .ToList() 
    .ForEach(g => Console.WriteLine("{0} : {1}", g.Key, g.Count())); 

Answer 4

var list = new List<int> { 1, 2, 10, 1, 23, 11, 1, 4, 2, 2, }; 
var groups = list.GroupBy(i => i); 
foreach (var group in groups) 
    Console.WriteLine("{0} occurs {1} times", group.Key, group.Count());