Question

需要通过IdCordinator对记录进行分组，条件

如果类别类型不等于“S”，则包含在组
如果特定协调员的类别类型为“S”且计数大于 1则包括在
如果特定协调员的类别类型为“S”且计数等于1，则不包括在组中

我应该如何构建我的where子句。如果我有一个如下的where子句，如果只有一个元素列表，虽然它不是“S”类，但它返回0条记录。

using System;
using System.Collections.Generic;
using System.Linq;

namespace LinqGroupbyWhere
{
    class Program
    {
        static void Main( string[] args )
        {
            StudentList studentList = new StudentList();
            studentList.getList();
            Console.ReadKey();
        }
    }

    public class StudentList
    {
        public void getList()
        {

            List<Students> stdLst = new List<Students>();
            stdLst.Add( new Students( "stud1", 20, "M", "I001" ) );
            stdLst.Add( new Students( "stud2", 20, "M", "I001" ) );
            stdLst.Add( new Students( "stud3", 20, "M", "I002" ) );
            stdLst.Add( new Students( "stud4", 20, "M", "I003" ) );
            stdLst.Add( new Students( "stud5", 20, "S", "I001" ) );
            stdLst.Add( new Students( "stud6", 20, "S", "I001" ) );
            stdLst.Add( new Students( "stud7", 20, "S", "I002" ) );

            var lst = stdLst.GroupBy( s => s.IdCordinator )
         .SelectMany( sg =>
                sg.Where( s => !s.Category.Equals( "S" ) || sg.Count( c => c.Category.Equals( "S" ) ) > 1 )
               .Select( student => student.Name ) )
               .OrderBy( o => o );

            Console.WriteLine( string.Join( ",", (string[]) lst.ToArray() ) );


        }
    }
    public class Students
    {

        public Students( string name, int age, string cat, string siCordinator )
        {
            this.Name = name;
            this.Age = age;
            this.Category = cat;
            this.IdCordinator = siCordinator;
        }
        public string Name
        {
            get;
            set;
        }
        public int Age
        {
            get;
            set;
        }
        public string Category
        {
            get;
            set;
        }
        public string IdCordinator
        {
            get;
            set;
        }
    }
}

Answer 1

你可以这样写它以获得你想要的输出：

var lst = stdLst.GroupBy(s => s.IdCordinator)
         .SelectMany(sg =>
                sg.Where(s => !s.Category.Equals("S") || sg.Count(c => c.Category.Equals("S")) > 1)
               .Select(student => student.Name))
               .OrderBy(o => o);

希望这能解决你的问题。

像这样更新你的构造函数：

public Students( string name, int age, string cat, string siCordinator )
{
    this.Name = name;
    this.Age = age;
    this.Category = cat;
    this.IdCordinator = siCordinator; // You were assiging same field to itself here, making it null
}

Linq groupby IdCordinator只有当categery类型计数大于1时

1 个答案: