带有键列表的 Dictionary 属性中的 Linq“分组依据”值

Question

我有以下对象列表

List<Obj> source = new List<Obj>();
source.Add(new Obj() { Name = "o1", Attributes = new Dictionary<string, string> { { "attA", "1" }, { "attB", "1" }, { "attC", "1" } } });
source.Add(new Obj() { Name = "o2", Attributes = new Dictionary<string, string> { { "attA", "1" }, { "attB", "2" }, { "attC", "1" } } });
source.Add(new Obj() { Name = "o3", Attributes = new Dictionary<string, string> { { "attA", "1" }, { "attB", "3" }, { "attC", "2" } } });
source.Add(new Obj() { Name = "o4", Attributes = new Dictionary<string, string> { { "attA", "1" }, { "attB", "4" }, { "attC", "2" } } });
source.Add(new Obj() { Name = "o5", Attributes = new Dictionary<string, string> { { "attA", "2" }, { "attB", "5" }, { "attC", "3" } } });
source.Add(new Obj() { Name = "o6", Attributes = new Dictionary<string, string> { { "attA", "2" }, { "attB", "6" }, { "attC", "3" } } });
source.Add(new Obj() { Name = "o7", Attributes = new Dictionary<string, string> { { "attA", "2" }, { "attB", "7" }, { "attC", "4" } } });
source.Add(new Obj() { Name = "o8", Attributes = new Dictionary<string, string> { { "attA", "2" }, { "attB", "8" }, { "attC", "4" } } });

所以我需要按特定属性的值对其进行分组，此外，这些属性的名称保存在单独的列表中，例如：

List<string> groupBy = new List<string>() { "attA", "attC" };

我尝试使用

var groups =
       from s in source
       group s by s.Attributes["attA"];

这很好，返回 2 个组：

• “1”-“o1 o2 o3 o4”
• “2”-“o5 o6 o7 o8”

但实际上我需要做的是按“attA”和“attC”（或 groupBy 变量中的任何内容）分组并获得以下四个组：

• “1_1”-“o1 o2”
• “1_2”-“o3 o4”
• “2_3”-“o4 o5”
• “2_4”-“o7 o8”

Answer 1

from c in source
group c by String.Join("_",groupBy.Select(gr=>c.Attributes[gr]).ToArray()) into gr
select new 
{
   AttrValues = gr.Key,
   //Values = gr.Key.Split('_'),
   Names = gr.Select(c=>c.Name).ToList()
};

组键是从 groupBy 键列表中获得的字典值的串联投影。

Answer 2

您可以按多个属性分组：

var groups = from s in source
             group s by new 
             { 
                AttributeA = s.Attributes["attA"], 
                AttributeC = s.Attributes["attC"] 
             };

//shows 4 groups
foreach (var group in groups)
    Console.WriteLine(group.Key.AttributeA + "_" + group.Key.AttributeC);