<div id="welcome">
    <asp:Label ID="lblUser" CssClass="roleCss" runat="server" Text=""></asp:Label>
    <asp:LinkButton ID="lbtnExit" CssClass="exit" Text="退出系统" runat="server" 
         onclick="lbtnExit_Click"></asp:LinkButton>
</div>
<div id="masterContent">
    <asp:ContentPlaceHolder id="ContentPlaceHolder1" runat="server">
        
    </asp:ContentPlaceHolder>
</div>

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            if (Session["user"] != null)
            {
                lblUser.Text = "欢迎您！" + Session["user"].ToString();
            }
            else
            {
                lblUser.Text = "您还没有登录！";
                lbtnExit.Text = "登录";
            }
        }
    }
    /// <summary>
    /// 退出系统
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void lbtnExit_Click(object sender, EventArgs e)
    {
        Session.Clear();
        //因为有框架，所以用JS跳转
        Response.Write("<script>this.parent.location='Login.aspx'</script>");//Login.aspx也位于网站根目录下
    }