请教c#简单的索引器问题

[chang_heng]

我是c#新手写了个程序一直报错 请大家帮我看看
using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

namespace 多个参数的索引器
{
//姓名,课程ID,成绩
class CourseScore //课程的分数类
{
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 //索引器,用于存取和查询CourseScore
{
private ArrayList arrCourseScore;
public CourseScoreIndexer()
{
arrCourseScore=new ArrayList();
}
public int this[string name, int courseID]
{
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));
}
}
}


class Program
{
static void Main(string[] args)
{
CourseScoreIndexer csi =new CourseScoreIndexer();
csi["张三",1]=90;
csi["张三",2]=80;
csi["张三",3]=85;
csi["李四",1]=80;
Console.WriteLine(csi["张三",2]);



}
}
}
错误信息 错误 1 “多个参数的索引器.CourseScoreIndexer.this[string, int].get”: 并非所有的代码路径都返回值 D:\Backup\我的文档\Visual Studio 2005\Projects\第二章\多个参数的索引器\多个参数的索引器\Program.cs 45 13 多个参数的索引器

[gomoku]

 
            get 
            { 
                foreach(CourseScore cs in arrCourseScore) 
                { 
                    if(cs.Name==name && cs.CourseID==courseID) 
                    { 
                        return cs.Score; 
                    } 
                    return -1; 
                } 
            } 

foreach当arrCourseScore的“长度”如果为零的时候，括号内的语句将不会执行，对不对？
也就是说return cs.Score; 或return -1;语句可能不会执行，这种情况下getter就没有返回值了。

因而编译器抱怨“并非所有的代码路径都返回值”。

[ljhcy99]

namespace 多个参数的索引器
{
//姓名,课程ID,成绩
class CourseScore //课程的分数类
{
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 //索引器,用于存取和查询CourseScore
{
private ArrayList arrCourseScore;
public CourseScoreIndexer()
{
arrCourseScore=new ArrayList();
}
public int this[string name, int courseID]
{
get

{
foreach(CourseScore cs in arrCourseScore)
{
if(cs.Name==name && cs.CourseID==courseID)
{
return cs.Score;
}
else continue;
}
return -1;
}
set
{
arrCourseScore.Add(new CourseScore(name,courseID,value));
}
}
}


class Program
{
static void Main(string[] args)
{
CourseScoreIndexer csi =new CourseScoreIndexer();
csi["张三",1]=90;
csi["张三",2]=80;
csi["张三",3]=85;
csi["李四",1]=80;
Console.WriteLine(csi["张三",2]);



}
}
}