C#集合中根据多个字段分组 group by linq表达式

 

 

void Main()
{
     var  empList =new List
     {
        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
        //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;}
}