当访问默认首页default.aspx时，会自动跳转到login.aspx页面上请求登录，随便输入用户名和密码，点击“登录”按钮，会回到首页，并显示当前登录的用户名。
Web.config
<configuration>
<system.web>
<compilation debug="true"/>
<authentication mode="Forms">
<forms loginUrl="login.aspx" name = ".ASPXFORMSAUTH" />
</authentication>
<authorization>
<deny users="?"/>
</authorization>
</system.web>
</configuration>
default.aspx
<HTML>
<HEAD>
<TITLE>首页</TITLE>
<script language="VB" runat="server">
Sub Page_Load(Sender As Object, e As EventArgs)
Message.Text = String.Format("你好，{0}", Context.User.Identity.Name)
End Sub
sub btnSignout_Click(Sender as Object, E as EventArgs)
FormsAuthentication.SignOut()
Response.Redirect("login.aspx")
end sub
</script>
</HEAD>
<BODY>
<asp:label id="Message" runat="server"/>
<br>
<form method="post" runat="server">
<asp:button id="btnSignout" Text="退出登录" runat="server" OnClick="btnSignout_Click"/>
</form>
</BODY>
</HTML>
login.aspx
<HEAD>
<TITLE>首页</TITLE>
<script lanugage="c#" runat="server">
private void Page_Load(object sender, EventArgs e)
{
if (Request.IsAuthenticated)
Response.Redirect("default.aspx");
}
void btnLogin_Click(Object sender, EventArgs e)
{
if (txtUsername.Text != null && txtUsername.Text != String.Empty && txtPassword.Text != null && txtPassword.Text != String.Empty)
FormsAuthentication.RedirectFromLoginPage(txtUsername.Text, true);
else
lblError.Text = "错误的用户名/密码";
}
</script>
</HEAD>
<BODY>
<form method="post" runat="server">
<asp:Label id="lblUsername" runat="server" Text="用户名："/>
<asp:Textbox id="txtUsername" runat="server"/>
<br>
<br>
<asp:Label id="lblPassword" runat="server" Text="密 码："/>
<asp:Textbox id="txtPassword" runat="server" TextMode="password"/>
<br>
<asp:button id="btnLogin" runat="server" Text="登录" OnClick="btnLogin_Click" />
</form>
<hr>
<br>
<asp:Label id="lblError" forecolor="red" runat="server"/>
</BODY>
</HTML>