c#这段代码怎么理解，谢谢

public class JZD
{
    public string JZDHANDLE;
    public string JZDBSM;
    public string JZDYSDM;
    public JZD()
    {
        JZDHANDLE = "";
        JZDBSM = "";
        JZDYSDM = "";
    }
    public string retrunVal(string ZDMC)
    {
        switch (ZDMC)
        {
            case "JZDHANDLE": return JZDHANDLE;
            case "JZDBSM": return JZDBSM;
            case "JZDYSDM": return JZDYSDM;
            default: return "";
        }
    }
}

不过定义了一个类，几个成员变量，然后一个构造函数而已，
核心方法只有下面这个，根据输入字符串，返回不同的成员变量

public string retrunVal(string ZDMC)
    {
        switch (ZDMC)
        {
            case "JZDHANDLE": return JZDHANDLE;
            case "JZDBSM": return JZDBSM;
            case "JZDYSDM": return JZDYSDM;
            default: return "";
        }
    }

//定义JZD类
public class JZD
{
public string JZDHANDLE;//定义成员变量
public string JZDBSM;//定义成员变量
public string JZDYSDM;//定义成员变量
//构造函数
public JZD()
{
JZDHANDLE = "";
JZDBSM = "";
JZDYSDM = "";
}
//自定义函数，根据参数不同，返回不同的成员变量
public string retrunVal(string ZDMC)
{
switch (ZDMC)
{
case "JZDHANDLE": return JZDHANDLE;
case "JZDBSM": return JZDBSM;
case "JZDYSDM": return JZDYSDM;
default: return "";
}
}
}