将Linq分组计数映射到C#实体

var result = from item in collection
             group item by item.Property into groupedItems
             select new
             {
                 Property = groupedItems.Key,
                 Count = groupedItems.Count()
             };

class Student
{
    public string Name { get; set; }
    public int Age { get; set; }
}

List<Student> students = new List<Student>
{
    new Student { Name = "Alice", Age = 20 },
    new Student { Name = "Bob", Age = 18 },
    new Student { Name = "Charlie", Age = 20 },
    new Student { Name = "David", Age = 22 },
    new Student { Name = "Eve", Age = 18 }
};

var result = from student in students
             group student by student.Age into groupedStudents
             select new
             {
                 Age = groupedStudents.Key,
                 Count = groupedStudents.Count()
             };

foreach (var item in result)
{
    Console.WriteLine($"Age: {item.Age}, Count: {item.Count}");
}

Age: 20, Count: 2
Age: 18, Count: 2
Age: 22, Count: 1