aspx

<%...@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="CheckUsernameWithAjax._Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>CheckUsernameWithAjax</title>
</head>
<body>
<form id="form" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true" />
Last Postback: <%= DateTime.Now %>
<br /><br />
<asp:Label ID="lblUserName" runat="server" AssociatedControlID="UserName">Desired Username</asp:Label>
<asp:TextBox ID="UserName" runat="server" CssClass="txt" onkeyup="usernameChecker(this.value);" />
<span id="spanAvailability"></span>

<script type="text/javascript">...
var usernameCheckerTimer;
var spanAvailability = $get("spanAvailability");
function usernameChecker(username) 
...{
clearTimeout(usernameCheckerTimer);
if (username.length == 0)
spanAvailability.innerHTML = "";
else
...{
spanAvailability.innerHTML = "<span style='color: #ccc;'>checking...</span>";
usernameCheckerTimer = setTimeout("checkUsernameUsage('" + username + "');", 750);
}
}
function checkUsernameUsage(username) 
...{
// initiate the ajax pagemethod call
// upon completion, the OnSucceded callback will be executed
PageMethods.IsUserAvailable(username, OnSucceeded);
}
// Callback function invoked on successful completion of the page method.
function OnSucceeded(result, userContext, methodName) 
...{
if (methodName == "IsUserAvailable")
...{
if (result == true)
spanAvailability.innerHTML = "<span style='color: DarkGreen;'>Available</span>";
else
spanAvailability.innerHTML = "<span style='color: Red;'>Unavailable</span>";
}
}
</script>
</form>
</body>
</html>
aspx.cs
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Web.Services;
namespace CheckUsernameWithAjax
...{
public partial class _Default : System.Web.UI.Page
...{
protected void Page_Load(object sender, EventArgs e)
...{
}
[WebMethod]
public static bool IsUserAvailable(string username)
...{
if (username.ToLower() == "storm")
return false;
else
return true;
}
}
}
本文介绍了一个使用ASP.NET和Ajax实现的实时用户名检查功能。该功能能够在用户输入用户名的同时,通过Ajax调用服务器端方法检查该用户名是否已被占用,并即时反馈结果。
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