在LINQ中适当使用关键字"new"

Question

请考虑以下代码:

string[] words =
{ "Too", "much", "of", "anything", "is" ,"good","for","nothing"};

var groups =from word in words
            orderby word ascending
            group word by word.Length into lengthGroups
            orderby lengthGroups.Key descending
           select new {Length=lengthGroups.Key, Words=lengthGroups};

   foreach (var group in groups)
   {
     Console.WriteLine("Words of length " + group.Length);
     foreach (string word in group.Words)
     Console.WriteLine(" " + word);
   }

为什么我们在这里需要关键字"new"？.你能给出一些其他简单的例子来正确理解它吗？

Answer 1

的new { A = "foo", B = "bar }语法定义了一个匿名类型与性质A和B时,分别用值"foo"的和"bar".您这样做是为了每行返回多个值.

没有某种新对象,你只能返回(例如)Key.要返回多个属性,需要值.在这种情况下,匿名类型很好,因为此数据仅用于此查询的本地.

您也可以定义自己的class,然后使用new它:

new MyType("abc", "def") // via the constructor

要么

new MyType { A = "abc", B = "def" } // via object initializer

除非MyType在此背景之外具有一些有用的含义,否则这是过度的.