public partial class SampleUser
  {
    string username;
    public string UserName
    {
      get { return username; }
      set { username = value; }
    }

    string userpwd;
    public string UserPWD
    {
      get { return userpwd; }
      set { userpwd = value; }
    }

    public override bool Equals(object obj)
    {
      SampleUser other = obj as SampleUser;
      if (other == null || other.UserName != this.UserName)
        return false;
      return true;
    }
  }

  public partial class SampleUser
  {
    public static List<SampleUser> userList = new List<SampleUser> {
      new SampleUser() { UserName = "01", UserPWD = "123"}, 
      new SampleUser() { UserName = "02", UserPWD = "123" }, 
      new SampleUser() { UserName = "03", UserPWD = "123" }, 
      new SampleUser() { UserName = "04", UserPWD = "123" }, 
    };

    public static SampleUser GetUser(string userName)
    {
      return userList.Find(u=>u.UserName == userName);
    }
  }

<authentication mode="Forms">
   <forms loginUrl="~/Login.aspx" defaultUrl="~/Default.aspx" />
  </authentication>
  <authorization>
   <deny users="?"/>
  </authorization>

<fieldset>
    <legend>用户登陆</legend>
    <div>
      用户名：<asp:TextBox ID="txtUserID" runat="server" Width="150" /><br /><br />
      密   码：<asp:TextBox ID="txtUserPWD" runat="server" TextMode="Password" Width="150" /><br /><br />
      <asp:CheckBox ID="cbSaveUserName" runat="server" Checked="true" Text="保持登录状态" />
    </div><br />
    <asp:Literal ID="ltMessage" Text="" runat="server" Visible="false" />
    <br />
    <p>
      <asp:Button ID="btnLogin" Text="登陆" runat="server" OnClick="btnLogin_Click" />
    </p>
  </fieldset>

protected void btnLogin_Click(object sender, EventArgs e)
    {
      string userID = this.txtUserID.Text.Trim();
      string userPWD = this.txtUserPWD.Text.Trim();

      SampleUser userEx = SampleUser.GetUser(userID);
      if (userEx == null)
      {
        ltMessage.Text = "用户不存在！";
        ltMessage.Visible = true;
        return;
      }

      if (userEx.UserPWD != userPWD)
      {
        ltMessage.Text = "用户名或密码错误，请重新输入！";
        ltMessage.Visible = true;
        return;
      }

      //添加票据，并将用户导航到默认页面
      FormsAuthentication.RedirectFromLoginPage(userEx.UserName, this.cbSaveUserName.Checked);
    }

 <authorization>
   <allow users="?"/>
  </authorization>

   <authorization>
    <deny users="?"/>
   </authorization>

<h2>
<p>用户名：<asp:Label ID="lblUserName" Text="" runat="server" /></p>
<p>密    码：<asp:Label ID="lblUserPWD" Text="" runat="server" /></p>
</h2>

if (this.Context.User != null && this.Context.User.Identity != null && this.Context.User.Identity.IsAuthenticated)
{
  SampleUser user = SampleUser.GetUser(this.Context.User.Identity.Name);
  if (user != null)
  {
    this.lblUserName.Text = user.UserName;
    this.lblUserPWD.Text = user.UserPWD;
  }
}

FormsAuthentication.SignOut();　　//退出登陆

<forms 
   name="name" 
   loginUrl="URL" 
   defaultUrl="URL"
   protection="[All|None|Encryption|Validation]"
   timeout="[MM]"
   path="path"
   requireSSL="[true|false]"
   slidingExpiration="[true|false]">
   enableCrossAppRedirects="[true|false]"
   cookieless="[UseUri|UseCookie|AutoDetect|UseDeviceProfile]" 
   domain="domain name"
   ticketCompatibilityMode="[Framework20|Framework40]">
   <credentials>...</credentials>
 </forms>