返回新的LINQ对象 [英] Return new LINQ object

问题描述

我想编写LINQ，它返回的新对象(字符串，整数)包含以下内容:

I want to write LINQ which return me new object(string, int) contains:

• 字符串(位置名称)
• int(职位数)

输出:

PositionA 8
PostionB  12
PostionC  13

这是我到目前为止所拥有的:

Here is what I have so far:

public List<string, int> TestL() //or IEnumerable?
{
    var q1 = TestList.GroupBy(s => s.Postion.ToUpper())
                     .Select(d =>
                           {
                               return new
                                   {
                                       NameDisplay = d.Key,
                                       Count = d.Count(s => s.PersonNR)
                                    };
                           })
                     .OrderBy(g => g.Key);
    return q1;
}

测试列表具有类似字段:位置，人名，城市，姓氏.所有字段都是 string .

TestList have fields like: Postion, PersonNR, City, LastName. All the fields are string.

推荐答案

您可能正在寻找元组.如果是C#7.3+，则可以尝试使用命名元组:

You, probably, are looking for a Tuple. In case of C# 7.3+ you can try using named tuples:

https://docs.microsoft.com/zh-cn/dotnet/csharp/tuples

 public IEnumerable<(string, int)> TestL() {
   return TestList
     .GroupBy(s => s.Postion.ToUpper())
     .Select(chunk => (NameDisplay: d.Key, Count: d.Count()))
     .OrderBy(item => item.NameDisplay); 
 }

在较旧的C#版本中，未命名之一:

In older C# versions unnamed one:

 public IEnumerable<Tuple<string, int>> TestL() {
   return TestList
     .GroupBy(s => s.Postion.ToUpper())
     .Select(chunk => Tuple.Create(d.Key, d.Count()))
     .OrderBy(item => item.Item1); 
 }

最后，您可以实现自定义类:

 public class MyClass {
   public MyClass(string nameDisplay, int count) {
     NameDisplay = nameDisplay;
     Count = count;
   }

   public string NameDisplay {get; private set;} 
   public int Count {get; private set;}
 } 

 ...


 public IEnumerable<MyClass> TestL() {
   return TestList
     .GroupBy(s => s.Postion.ToUpper())
     .Select(chunk => new MyClass(d.Key, d.Count()))
     .OrderBy(item => item.NameDisplay); 
 }

如果您要返回的不是 IEnumerable< T> ，而是 List< T> ，请在之后添加 .ToList().OrderBy(...)

In case you want to return not IEnumerable<T> but List<T>, add .ToList() after .OrderBy(...)

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