我在处理Linq(左联接 - 分组 - 计数)时遇到了困难,请帮助我。 以下是我的代码,它给出了这个结果。
Geography 2
Economy 1
Biology 1
I'm expecting this...
Geography 2
Economy 1
Biology 0
我该怎么解决这个问题?
class Department
{
public int DNO { get; set; }
public string DeptName { get; set; }
}
class Student
{
public string Name { get; set; }
public int DNO { get; set; }
}
class Program
{
static void Main(string[] args)
{
List<Department> departments = new List<Department>
{
new Department {DNO=1, DeptName="Geography"},
new Department {DNO=2, DeptName="Economy"},
new Department {DNO=3, DeptName="Biology"}
};
List<Student> students = new List<Student>
{
new Student {Name="Peter", DNO=2},
new Student {Name="Paul", DNO=1},
new Student {Name="Mary", DNO=1},
};
var query = from dp in departments
join st in students on dp.DNO equals st.DNO into gst
from st2 in gst.DefaultIfEmpty()
group st2 by dp.DeptName into g
select new
{
DName = g.Key,
Count = g.Count()
};
foreach (var st in query)
{
Console.WriteLine("{0} \t{1}", st.DName, st.Count);
}
}
}