如何在LINQ

Question

这是我写的一些代码。变量aa具有一组不明显的值。我想aa是一组不同的值，所以我需要一个“分组”。我遇到的问题是“new”变量是一个动态创建的字符串，在完成新的操作之前我无法对其进行分组。

List<KeyValuePair<String, int>> x = new List<KeyValuePair<string, int>>();
x.Add(new KeyValuePair<String, int>("one", 1));
x.Add(new KeyValuePair<String, int>("two", 2));

List<KeyValuePair<String, int>> y = new List<KeyValuePair<string, int>>();
y.Add(new KeyValuePair<String, int>("one", 1));
y.Add(new KeyValuePair<String, int>("xxx", 12));

var aa = from xx in x
         from yy in y
         select new { AA = string.Format("a={0}, b={1}", xx, yy) };

Answer 1

可以使用Distinct()

//This var can be exchanged with IEnumerable<string> 
var aa = (from xx in x
          from yy in y
          select string.Format("a={0}, b={1}", xx, yy))
          .Distinct();

如果你想让列表x的内容在y上排除，或者你的内容在x上独占，你就拥有Except()

命令

var aa1 = from xx in x
         from yy in y
         select new { AA = string.Format("a={0}, b={1}", xx, yy) };
/*RESULT:
a=[one, 1], b=[one, 1]
a=[one, 1], b=[xxx, 12]
a=[two, 2], b=[one, 1]
a=[two, 2], b=[xxx, 12]*/

var aa2 = from xx in x
         from yy in y.Except(x)
         select new { AA = string.Format("a={0}, b={1}", xx, yy) };
/*RESULT:
a=[one, 1], b=[xxx, 12]
a=[two, 2], b=[xxx, 12]*/

var aa3 = from xx in x.Except(y)
         from yy in y
         select new { AA = string.Format("a={0}, b={1}", xx, yy) };
/*RESULT:
a=[two, 2], b=[one, 1]
a=[two, 2], b=[xxx, 12]*/

var aa4 = from xx in x.Except(y)
         from yy in y.Except(x)
         select new { AA = string.Format("a={0}, b={1}", xx, yy) };
/*RESULT:
a=[two, 2], b=[xxx, 12]*/

Answer 2

是的，你可以用aa.ToList（）实现，然后分组。但你至少应该说出你期望的输出