/// 
要查询的对象
class Employee {   public int ID { get;set; }   public string FName { get; set; }   public int Age { get; set; }   public char Sex { get; set; }}

如果对这个类的Age和Sex的连个字段进行分组，方法如下：

// 先造一些数据List
    
      empList = new List
     
      ();empList.Add(new Employee() {   ID = 1, FName = "John", Age = 23, Sex = 'M'});empList.Add(new Employee() {   ID = 2, FName = "Mary", Age = 25, Sex = 'F'});empList.Add(new Employee() {   ID = 3, FName = "Amber", Age = 23, Sex = 'M'});empList.Add(new Employee() {   ID = 4, FName = "Kathy", Age = 25, Sex = 'M'});empList.Add(new Employee() {   ID = 5, FName = "Lena", Age = 27, Sex = 'F'});empList.Add(new Employee() {   ID = 6, FName = "Bill", Age = 28, Sex = 'M'});empList.Add(new Employee() {   ID = 7, FName = "Celina", Age = 27, Sex = 'F'});empList.Add(new Employee() {   ID = 8, FName = "John", Age = 28, Sex = 'M'});
     
    

接下来的做法是：

// 实现多key分组的扩展函数版本var sums = empList         .GroupBy(x => new { x.Age, x.Sex })         .Select(group => new {            Peo = group.Key, Count = group.Count()         });foreach (var employee in sums) {   Console.WriteLine(employee.Count + ": " + employee.Peo);}// 实现多key分组的lambda版本var sums2 = from emp in empList            group emp by new { emp.Age, emp.Sex } into g            select new { Peo = g.Key, Count = g.Count() };foreach (var employee in sums) {   Console.WriteLine(employee.Count + ": " + employee.Peo);}

这个例子中就充分利用了匿名类型