…
asp:TextBox ID="txtUser_Id" runat="server" MaxLength="4" Width="120px" BorderColor="LightSlateGray" BorderWidth="1px">/asp:TextBox>
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asp:ImageButton ID="btnInsert" runat="server" ImageUrl="~/Images/Login.GIF" OnClick="btnInsert_Click" />
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asp:CheckBox ID="cbxRemeberUser" runat="server" Text="记住用户名" Font-Size="Small" ForeColor="gray"/>
…

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            this.txtUser_Id.Focus();
            if (!Object.Equals(Request.Cookies["UserID"], null))
            {
                //创建一个Cookie对象，实现记住用户名
                HttpCookie readcookie = Request.Cookies["UserID"];
                this.txtUser_Id.Text = readcookie.Value;
            }
        }
    }
    private void CreateCookie()
    {
        //创建一个Cookie对象
        HttpCookie cookie = new HttpCookie("UserID");
        //判断Checkbox控件是否被选中
        if (this.cbxRemeberUser.Checked)
        {
            //将用户编号存储到创建的Cookie对象中
            cookie.Value = this.txtUser_Id.Text;
        }
        //获取创建的Cookie对象的过期时间
        cookie.Expires = DateTime.MaxValue;
        //将创建的Cookie对象添加到内部Cookie集合中
        Response.AppendCookie(cookie);
}

    protected void btnInsert_Click(object sender, ImageClickEventArgs e)
    {
…
        if (object.Equals(Request.Cookies["UserID"], null))
        {
          //调用自定义方法 CreateCookie()存储用户名
          CreateCookie();
        }
        else
        {
           CreateCookie();
        }
…
}