Linq 中按照多個值進行分組(GroupBy)

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

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

// 實現多key分組的擴展函數版本
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);
}

// 實現多key分組的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);
}

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