Asp.Net自学笔记...(索引器的使用)

嘿嘿``这个终于完成咯..妈哟`乱想的程序`在实现过程中.还是遇到个小麻烦..
Web编程和Win32编程`区别还是蛮大的嘛..虽然Asp.Net也是面像对象..但是还是
有区别..我今天就深深的体会到了哈!
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public partial class _Default : System.Web.UI.Page
{
    //创建一个类...
    public class admin
    {
        public string[] sun; //创建一个动态数组..公有成员..方便后面演示..
        //private string sun1; //取得输入值的变量..

        //定义一个构造函数...
        public admin(int ToSun,string sun1)
        {
            //使用循环给数组赋值..
            sun = new string[ToSun]; //读取用户选择的上标值.并初始数组．．．
            for (int i = 0; i < ToSun; i++)
            {
                sun[i] = "数组[" + Convert.ToString(i) + "]的值是" + sun1;
            }
        }

        //定义一个索引器( public 数据类型 this[int index] )
        public string this[int index] 
        {
            get  //返回值..
            { return sun[index]; }
            set //写入值..
            {
                if (sun[index]!=null)
                {
                    sun[index]=value;
                }
            }
        }

        }

        protected void Button1_Click(object sender, EventArgs e)
    {
        admin a = new admin(Convert.ToInt32(DropDownList1.Text),TextBox1.Text); //创建对象...
        //利用循环读出索引中的值...
        for (int i=0;i<a.sun.Length;i++)
        {
            Response.Write(a[i]+"<br>");
        }
        Response.Write("<br>程序创建了" + a.sun.Length + "个数组.");
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        //初始下拉列表筐的值!
        for (int i = 0; i < 50; i++)
        {
            DropDownList1.Items.Add(Convert.ToString(i));
        }
    }

    protected void Button2_Click(object sender, EventArgs e)
    {
        if (TextBox2.Text != "")
        {
            admin a = new admin(Convert.ToInt32(DropDownList1.Text), TextBox1.Text); //创建对象...
            //利用循环读出索引中的值...
            int index = 0; //取得用户选择的下标..必须赋予初始值．．否则无法后面无法调用．我也不知道为什么．郁闷．
            for (int i = 0; i < a.sun.Length; i++)
            {
                index = Convert.ToInt32(DropDownList2.Text);
                if (i == index)
                {
                    a[i] = "数组[" + Convert.ToString(i) + "]的值是" + TextBox2.Text;
                }
                Response.Write(a[i] + "<br>");
            }
            Response.Write("<br>数组[" + index + "]的值已被修改为" + TextBox2.Text);
        }
        else
        {
            Response.Write("请先生成数据．．");
        }
    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        for (int i = 0; i <= Convert.ToInt32(DropDownList1.Text); i++)
        {
            DropDownList2.Items.Add(Convert.ToString(i));
        }
    }
    protected void DropDownList1_TextChanged(object sender, EventArgs e)
    {
        DropDownList2.Items.Clear();
        for (int i = 0; i <= Convert.ToInt32(DropDownList1.Text); i++)
        {
            DropDownList2.Items.Add(Convert.ToString(i));
        }
    }
}
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