Login Logout using Forms authentication with master page

 Create login.aspx page

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">

    <asp:TextBox runat="server" ID="txtUsername" /><br />

    <asp:TextBox runat="server" ID="txtPassword" />

    <asp:Button runat="server" ID="btnLogin" Text="Log in" OnClick="btnLogin_Click" />

    <asp:Label runat="server" ID="lblStatus"  />

</asp:Content>

login.aspx.cs page

protected void Page_Load(object sender, EventArgs e)

        {

//If user is already login, it will redirect to Homenew.aspx page, with below code

            if (HttpContext.Current.User.Identity.IsAuthenticated)

            {

                Response.Redirect("Homenew.aspx");

            }

        }

        protected void btnLogin_Click(object sender, EventArgs e)

        {

            if(txtUsername.Text== "12" && txtPassword.Text== "12")

            {

                FormsAuthentication.RedirectFromLoginPage(txtUsername.Text, true);

            }

            else

            {

                lblStatus.Text="Incorrect password or id";

            }

        }

----------------------

Create Homenew.aspx page

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">

   

    <h1>Welcome</h1>

    <h1><asp:Label runat="server" ID="lblWelcome" ></asp:Label></h1>

  </asp:Content>

Homenew.aspx.cs 

 protected void Page_Load(object sender, EventArgs e)

        {

            //For showing current user name

                lblWelcome.Text =  Context.User.Identity.Name  ;

            

        }

Also a sign out button will be created which will be inside form tag (runat server)

aspx.cs

 protected void logout_Click(object sender, EventArgs e)

        {

            FormsAuthentication.SignOut();

         

            Response.Redirect("loginnew.aspx");

        }

aspx

<form id="form1" runat="server">

 <asp:LinkButton OnClick="logout_Click" runat="server" class="nav_link"> <i class='bx bx-log-out nav_icon'></i> <span class="nav_name">SignOut</span> </asp:LinkButton>

</form>

-----------

In web.config 

<system.web>

  <authentication mode="Forms">

  <forms loginUrl="loginnew.aspx" defaultUrl="Homenew.aspx"   name=".ASPXFORMSAUTH"></forms>

  </authentication>

  <authorization>

  <deny users="?" />

  </authorization>

<system.web>

<system.webServer>

    <defaultDocument>

      <files>

        <add value="loginnew.aspx" />

      </files>

    </defaultDocument>

</system.webServer>

reference:- https://www.c-sharpcorner.com/UploadFile/fa9d0d/forms-authentication-in-Asp-Net/

https://www.aspsnippets.com/Articles/Implement-Role-based-security-using-Forms-Authentication-in-ASPNet.aspx

https://www.codeproject.com/Articles/2905/Role-based-Security-with-Forms-Authentication