Linq 中按照多个值进行分组(GroupBy)

.GroupBy(x => new { x.Age, x.Sex })

group emp by new { emp.Age, emp.Sex } into g

// 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);
}

转自 http://www.cnblogs.com/beginor/archive/2009/04/24/1442939.html