logout using link button in asp.net c#

Question

i want when user click on logout its logout and it shows again Register and login option..

 

here is my code..

<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav navbar-right">
<li><a href="#page-top" class="page-scroll">Home</a></li>
<li><a href="#about" class="page-scroll">About</a></li>
<li><a href="#contact" class="page-scroll">Contact</a></li>
<div class="dropdown">
<asp:LinkButton ID="lnkUserName" runat="server" Text="Register Her...!" OnCommand="lnkUserName_Command"></asp:LinkButton>
<div class="dropdown-content">
<asp:LinkButton ID="LinkButton1" runat="server" Text="Login...!" OnCommand="LinkButton1_Command"></asp:LinkButton>
</div>
</div>
</ul>
</div>

protected void Page_Load(object sender, EventArgs e)
{
if(Session["UserName"]!=null)
{
string query = "select * from User where UserName'" + Session["UserName"] + "'";
lnkUserName.Text = string.Format("Welcome {0}", Session["UserName"].ToString());
LinkButton1.Text = string.Format("Logout");
lnkUserName.PostBackUrl = "Profile.aspx";
}
}
protected void lnkUserName_Command(object sender, CommandEventArgs e)
{
Response.Redirect("/SignIn.aspx");
}
protected void LinkButton1_Command(object sender, CommandEventArgs e)
{
if (LinkButton1.Text == "Logout")
{
Session["UserName"] = "";
Response.Redirect("/Walpaper.aspx");
}
else
{
Response.Redirect("/Login.aspx");
}