构造器练习，对着教学视频敲的，熟悉一下吧

using System;
using System.Collections; //要用ArrayList要引用这个
class CourseScore {  //普通的属性用法
    private string name;
    private int courseID;
    private int score;
    public CourseScore(string name, int courseID, int score) {
        this.name = name;
        this.courseID = courseID;
        this.score = score;
    }
    public string Name {
        get { return name; }
        set { name = value; }
    }
    public int CourseID {
        get { return courseID; }
        set { courseID = value; }
    }
    public int Score {
        get { return score; }
        set { score = value; }
    }
}
class CourseScoreIndexer {  //构造器
    private ArrayList arrCourseScore;
    public CourseScoreIndexer() {
        arrCourseScore = new ArrayList();
    }
    public int this[string name, int courseID] {  //构造器只能用this
        get {
            foreach (CourseScore cs in arrCourseScore) {
                if (cs.Name == name && cs.CourseID == courseID) {
                    return cs.Score;
                }
            }
            return -1;
        }
        set {
            arrCourseScore.Add(new CourseScore(name, courseID, value));  //hashtable用.Add
        }
    }
    public ArrayList this[string name] {
        get {
            ArrayList tempArr = new ArrayList();
            foreach (CourseScore cs in arrCourseScore) {
                if (cs.Name == name) {
                    tempArr.Add(cs);
                }
            }
            return tempArr;
        }
    }
}
class Test {
    static void Main() {
        CourseScoreIndexer csi = new CourseScoreIndexer();
        csi["张三", 1] = 90;
        csi["张三", 2] = 80;
        csi["李四", 1] = 70;
        Console.WriteLine("张三的第2门课程分数为：" + csi["张三", 2]);
        ArrayList tempArr = csi["张三"];
        foreach (CourseScore cs in tempArr) {
            Console.WriteLine("姓名：" + cs.Name + "  课程编号：" + cs.CourseID + "  分数：" + cs.Score);
        }
        Console.ReadKey();
    }
}