代码解释！专业人士请进！

小弟新手，请多关照，跪谢了，急用！
protected string show_admin(int id)
    {
        if (Session["admin"] != null)
        {
            return "<a href=re.aspx?id=" + id + ">回复</a>" + "&nbsp;&nbsp;&nbsp;<a href=del.aspx?id=" + id + ">删除</a>";
        }
        else
        {
            return null;
        }
    }
    protected void addly_Click(object sender, EventArgs e)
    {
        book binbin = new book();
        binbin.username = Server.HtmlEncode(this.username.Text);
        binbin.email = this.email.Text;
        binbin.qq = this.qq.Text;
        binbin.homepage = this.homepage.Text;
        if (this.Radboy.Checked)
        {
            binbin.sex = "男";
            binbin.face = "boy";
        }
        else
        {
            binbin.sex = "女";
            binbin.face = "gril";
        }
        binbin.body = this.lybody.Text;
        if (this.ishde.Checked)
        {
            binbin.ishide = true;
        }
        else
        {
            binbin.ishide = false;
        }
        Label1.Text = binbin.ishide.ToString();
        if (saveinfo.savely(binbin))
        {
            Response.Redirect("lyb.aspx");
        }
        else
        {
            Response.Write("<script>alert('留言失败,服务器错误!');location.herf='lyb.aspx'");
        }
    }