c# - 如何通过 lambda/方法表达式使用 linq 创建嵌套组

Question

这可能吗？例如，您将如何使用 lambda 表达式重写下面的工作代码？

public void QueryNestedGroups()
{
    var queryNestedGroups =
        from student in students
        group student by student.Year into newGroup1
        from newGroup2 in
            (from student in newGroup1
            group student by student.LastName)
        group newGroup2 by newGroup1.Key;
}

// Three nested foreach loops are required to iterate  
// over all elements of a grouped group. Hover the mouse  
// cursor over the iteration variables to see their actual type. 
foreach (var outerGroup in queryNestedGroups)
{
    Console.WriteLine("DataClass.Student Level = {0}", outerGroup.Key);
    foreach (var innerGroup in outerGroup)
    {
        Console.WriteLine("\tNames that begin with: {0}", innerGroup.Key);
        foreach (var innerGroupElement in innerGroup)
        {
            Console.WriteLine("\t\t{0} {1}", innerGroupElement.LastName, innerGroupElement.FirstName);
        }
    }
}

Answer 1

var names = myClass1List
    .SelectMany(c1 => c1.Class2List.Where(c2 => c2.Name == "something"))
    .SelectMany(c2 => c2.Class3List.Select(c3 => c3.Name));

var names = myClass1List
    .SelectMany(c1 => c1.Class2List
        .Where(c2 => c2.Name == "something")
        .SelectMany(c2 => c2.Class3List
            .Select(c3 => c3.Name)));

查看更多:LINQ on List with lot of nested List