C# 使用 Group By Linq 进行计数
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原文地址: http://stackoverflow.com/questions/12270018/
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Counting Using Group By Linq
提问by Nick LaMarca
I have an object that looks like this:
我有一个看起来像这样的对象：
Notice
{
string Name,
string Address
}
In a List<Notice>I want to output All distinct Name and how many times the particular appears in the collection.
在List<Notice>我想输出所有不同的名称以及特定在集合中出现的次数。
For example:
例如：
Notice1.Name="Travel"
Notice2.Name="Travel"
Notice3.Name="PTO"
Notice4.Name="Direct"
I want the output
我想要输出
Travel - 2
PTO - 1
Direct -1
I can get the distinct names fine with this code but I can't seem to get the counts all in 1 linq statement
我可以使用此代码获得不同的名称，但似乎无法在 1 条 linq 语句中获得所有计数
theNoticeNames= theData.Notices.Select(c => c.ApplicationName).Distinct().ToList();
采纳答案by Leniel Maccaferri
var noticesGrouped = notices.GroupBy(n => n.Name).
Select(group =>
new
{
NoticeName = group.Key,
Notices = group.ToList(),
Count = group.Count()
});
回答by Jon Skeet
A variation on Leniel's answer, using a different overload of GroupBy:
Leniel 答案的变体，使用了不同的重载GroupBy：
var query = notices.GroupBy(n => n.Name,
(key, values) => new { Notice = key, Count = values.Count() });
Basically it just elides the Selectcall.
基本上它只是忽略了Select调用。
