C#集合中根据多个字段分组 group by linq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'}
     };
       
　　//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;}
}