在ASP.NET Web Forms中，我们可以使用以下步骤实现“记住我”功能。

1. 在登录页的复选框中添加“记住我”的选项。

2. 在验证用户凭据时，检查是否选中了“记住我”的复选框，并根据情况设置持久性cookie。

protected void btnLogin_Click(object sender, EventArgs e)
{
    if (Membership.ValidateUser(txtUsername.Text, txtPassword.Text))
    {
        if (chkRememberMe.Checked)
        {
            HttpCookie cookie = new HttpCookie("myAppCookie");
            cookie.Values.Add("username", txtUsername.Text.Trim());
            cookie.Expires = DateTime.Now.AddDays(30);
            Response.Cookies.Add(cookie);
        }
        FormsAuthentication.RedirectFromLoginPage(txtUsername.Text, false);
    }
}

3. 在应用程序的Global.asax.cs文件中，使用FormsAuthentication_OnAuthenticate事件处的代码检查cookie，并为经过身份验证的用户设置新的FormsAuthenticationTicket。

protected void FormsAuthentication_OnAuthenticate(object sender, FormsAuthenticationEventArgs args)
{
    if (Request.Cookies["myAppCookie"] != null)
    {
        HttpCookie cookie = Request.Cookies["myAppCookie"];
        string username = cookie.Values["username"];

        if (!string.IsNullOrEmpty(username))
        {
            MembershipUser user = Membership.GetUser(username);

            if (user != null)
            {
                FormsAuthenticationTicket authTicket = new FormsAuthenticationTicket(
                    1, 
                    user.UserName, 
                    DateTime.Now, 
                    DateTime.Now.AddDays(30), 
                    true, 
                    user.UserId.ToString());

                string encryptedTicket = FormsAuthentication.Encrypt(authTicket);

                HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName, encryptedTicket);
                HttpContext.Current.Response.Cookies.Add(cookie);

                args.User = new System.Security.Principal.GenericPrincipal(new FormsIdentity(authTicket), new string[] { });
            }
        }
    }
}

通过这些步骤，我们可以在ASP.NET Web Forms中实现“记