ASP初学者登录和注销帮助

问题1:登录页面-如果用户输入错误的信息，我希望出现一个弹出窗口，提示重新输入凭据。

问题2:注销功能-当用户单击注销按钮时，我需要结束用户会话。有人能告诉我在Logout.aspx和Logout.aspx页面中放什么吗？

登录页面的代码隐藏：

   protected void btnLogin_Click1(object sender, EventArgs e)
    {
        ThisWS.Client client = new ThisWS.Client();
        //client.Endpoint.Address = new System.ServiceModel.EndpointAddress("https://svcThisService.svc/soap");
        WSAccess.ThisWS.clsTypesAuthResult response = client.Auth(this.txtUsername.Text, this.txtPassword.Text, txtAuthCode.Text);
        client.Close();
        this.lblErrorMessage.Text = response.Error;
        this.lblToken.Text = response.Token.ToString();
        int?[] cases = response.CaseNum;
        //Session.Add("Username", this.txtUsername.Text);   //User must re-login after an hour, since the token expires.
        //Session.Add("Password", this.txtPassword.Text);
        //Session.Add("AuthCode", this.txtAuthCode.Text);
        Session.Add("Token", response.Token);
        Session.Add("TokenExpires", DateTime.Now.AddHours(1));
        Session.Add("Cases", cases);
        Session.Add("PartyNameId", response.PartyNameID);
        Response.Redirect("ListCases.aspx");

.我有登录表单的ASPX代码：

<p class="redtext">Please use the form below to login.</p>
 <div class="">
<form id="form1" runat="server">
<div>
    <table class="auto-style1">
        <tr>
            <td class="auto-style2">Your Username:</td></tr>
        <tr>
            <td>
                <asp:TextBox ID="txtUsername" runat="server" Width="241px" MaxLength="255"></asp:TextBox>
            </td>
            <td>&nbsp;</td>
        </tr>
        <td>&nbsp;</td>
        <tr>
            <td class="auto-style2">Your Password:</td></tr>
        <tr>
            <td>
                <asp:TextBox ID="txtPassword" runat="server" Width="239px"></asp:TextBox>
            </td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td class="auto-style2" hidden="hidden">Authentication code: </td>
            <td>
                <asp:Label ID="txtAuthCode" runat="server" Width="244px" Visible="False">000</asp:Label>
            </td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td>
                <asp:Button ID="btnLogin" runat="server" Text="Click Here to Login" class="btn btn-primary btn-block" Width="175px" OnClick="btnLogin_Click1" />
            </td>
            <td>&nbsp;</td>
        </tr>
       </table>
</div>
</form> 
</div>

<asp:Button ID="btnLogin" runat="server" Text="Click Here to Login" class="btn btn-primary btn-block" Width="175px" OnClick="verifyCredentials()" />

function verifyCredentials() {
    if ( credentials != correctCredentials ) {
          alert('Please Enter Correct Credentials')
    else
          //proceed

element.addEventListener(type, handler, false);

$('#btnLogin').click(function() { ..... });