asp.net学习时发现取不到文本框的值？

我新建的一个 .ascx文件，在里面加了几个文本框，但我取不到值，是怎么回事，应该怎么取值?以下是我的代码:
C# code:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using Web.test.Model;
public partial class editPage : System.Web.UI.UserControl
{
public string id
{
set { this.txtId.Text = value; }
get { return this.txtId.Text; }
}
public string title
{
set { this.txtTitle.Text = value; }
get { return this.txtTitle.Text; }
}
public string keyWord
{
set { this.txtKeyword.Text = value; }
get { return this.txtKeyword.Text; }
}
public string descript
{
set { this.txtContent.Text = value; }
get { return this.txtContent.Text; }
}

Article a = new Article();
protected void Page_Load(object sender, EventArgs e)
{
string id=Request.QueryString["ID"];
this.a = MoreTableDAO.findDetailByID(Convert.ToInt32(id));
txtId.Text = Convert.ToString(a.articleId);
txtTitle.Text = this.a.title;
txtKeyword.Text = this.a.keyWord;
txtContent.Text = this