C# GroupBy 并计算 List 中的唯一元素
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GroupBy and count the unique elements in a List
提问by Jason94
I have a list that contains only strings. What I would love to do is group by and return a count.
我有一个只包含字符串的列表。我想做的是分组并返回一个计数。
For instance:
例如：
Foo1
Foo2
Foo3
Foo1
Foo2
Foo2
Would result in Foo1: 2, Foo2: 3, Foo3: 1. I've tried with Linq but the list has a GroupBy that might do the trick but i messed it up, can't figure the use :(
会导致 Foo1: 2, Foo2: 3, Foo3: 1. 我试过使用 Linq 但列表中有一个 GroupBy 可能会起作用，但我搞砸了，无法弄清楚用途:(
采纳答案by Serj-Tm
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() });
回答by Royi Namir
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);
回答by HW90
var grouped = select new
{
Foo= grp.Key,
Bar= grp.Select(x => x.SomeField).Distinct().Count()
};
a working example with the NorthWind database so that you can check::
NorthWind 数据库的工作示例，以便您可以检查：
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>");
}
Hereyou can find a very good example
在这里你可以找到一个很好的例子
回答by Igor Gorjanc
A good solution is available on http://msdn.microsoft.com/en-us/library/vstudio/bb534304(v=vs.100).aspxIt groups data by key; each key has it's own list of data you can iterate over it.
一个好的解决方案可在http://msdn.microsoft.com/en-us/library/vstudio/bb534304(v=vs.100).aspx这组由关键数据; 每个键都有自己的数据列表，您可以对其进行迭代。
