C#集合中根据多个字段分组groupbylinq表达式void Main()
{
var  empList =new List<Employee>
{
new Employee {ID = 1, FName = "John", Age = 23, Sex = 'M'},
new Employee {ID = 2, FName = "Mary", Age = 25, Sex = 'F'},
new Employee {ID = 3, FName = "Amber", Age = 23, Sex = 'M'},
new Employee {ID = 4, FName = "Kathy", Age = 25, Sex = 'F'},
new Employee {ID = 5, FName = "Lena", Age = 27, Sex = 'F'},
new Employee {ID = 6, FName = "Bill", Age = 28, Sex = 'M'},
new Employee {ID = 7, FName = "Celina", Age = 27, Sex = 'F'},
new Employee {ID = 8, FName = "John", Age = 28, Sex = 'M'}
groupby分组};
  //这⾥是根据Age,Sex进⾏分组
// query with lamda expression g.Key代表Age和Sex两字段，Count为新增字段 // 最终返回的集合QueryWithLamda包含字段：Age、Sex、Count var QueryWithLamda = empList.GroupBy(x => new { x.Age,  x.Sex})
.Select(g=>new {g.Key, Count=g.Count()});
//query with standard expression<br>        //返回结果同上
var query=from el in empList
group el by new {el.Age,el.Sex} into g
select new {g.Key, Count=g.Count()};
foreach (var employee in query /* Or  QueryWithLamda */ )
Console.WriteLine(employee.Count);
}
public class Employee
{
public int ID {get;set;}
public string FName {get;set;}
public int Age {get;set;}
public char Sex {get;set;}
}