使用LINQ对字典中的键和值进行排序

Question

我刚刚写了一些代码，将数据添加到这个字典中：

    Dictionary<string, Dictionary<string, double>> studentsExamsMarks = 
        new Dictionary<string, Dictionary<string, double>>();
        studentsExamsMarks.Add("Peter", new Dictionary<string, double>());
        studentsExamsMarks["Peter"].Add("History", 5.15);
        studentsExamsMarks["Peter"].Add("Biology", 4.20);
        studentsExamsMarks["Peter"].Add("Physics", 4.65);
        studentsExamsMarks.Add("John", new Dictionary<string, double>());
        studentsExamsMarks["John"].Add("History", 6.00);
        studentsExamsMarks["John"].Add("Biology", 3.75);
        studentsExamsMarks["John"].Add("Physics", 4.15);
        studentsExamsMarks.Add("Michael", new Dictionary<string, double>());
        studentsExamsMarks["Michael"].Add("History", 3.00);
        studentsExamsMarks["Michael"].Add("Biology", 3.95);
        studentsExamsMarks["Michael"].Add("Physics", 4.95);

我应该如何首先按照学生的名字（升序）排序和打印，而不是按照内部词典中的双精度值或主题的名字排序和打印？如果你给我看两个版本，我将不胜感激。非常感谢。

Answer 1

您可以使用SelectMany获取所有内部字典条目，以创建具有所有属性的匿名类型。则OrderBy和ThenBy:的排序很简单

var ordered = studentsExamsMarks
    .SelectMany(kv => kv.Value
        .Select(kvInner => new {Name = kv.Key, Subject = kvInner.Key, Value = kvInner.Value}))
    .OrderBy(x => x.Name)
    .ThenBy(x => x.Value);  // use x.Subject if you want to order by that instead
foreach (var x in ordered)
    Console.WriteLine($"{x.Name} {x.Subject} {x.Value}");