c# - GroupBy 并计算 List 中的唯一元素

Question

我有一个只包含字符串的列表。我想做的是分组并返回计数。

例如：

Foo1
Foo2
Foo3
Foo1
Foo2 
Foo2

会导致 Foo1: 2, Foo2: 3, Foo3: 1。我尝试过使用 Linq，但列表中有一个 GroupBy 可能会解决问题，但我搞砸了，不知道用途:(

Answer 1

var list = new List<string> { "Foo1", "Foo2", "Foo3", "Foo2", "Foo3", "Foo3", "Foo1", "Foo1" };

var grouped = list
    .GroupBy(s => s)
    .Select(group => new { Word = group.Key, Count = group.Count() });

Answer 2

 var items= myList
    .GroupBy(g => g)
    .Select(t => new {count= t.Count(), key= t.Key });

 foreach (var group in items)
     Console.WriteLine ( group.key + " " + group.count);

Answer 3

   var grouped =  select new
     {
         Foo= grp.Key,
         Bar= grp.Select(x => x.SomeField).Distinct().Count()
     };

NorthWind 数据库的工作示例，以便您检查::

    NWindCustomersDataContext dc = new NWindCustomersDataContext();


    var query = (from c in dc.Customers
                 join o in dc.Orders on c.CustomerID equals o.CustomerID
                 group o by c.CustomerID into g
                 select new
                 {
                     CustomerID = g.Key,
                     Company = (from cust in dc.Customers
                               where cust.CustomerID == g.Key
                               select cust).ToList(),
                     Count = g.Select(x => x.OrderID).Distinct().Count()
                 }).OrderByDescending(y => y.Count);




    foreach (var item in query)
    {
        Response.Write("CustomerID: " + item.CustomerID + "</br>" + "CompanyName: " + item.Company[0].CompanyName.ToString() + "</br>");


    }

在这里你可以找到一个很好的例子

Answer 4

http://msdn.microsoft.com/en-us/library/vstudio/bb534304(v=vs.100).aspx提供了一个很好的解决方案 。每个键都有自己的数据列表，您可以对其进行迭代。