Saturday, December 08, 2007 - 文章

之前寫過一篇介紹在UpdatePanel動態更新時觸發Javascript的方法，不過有網友反應不清楚實作的細節，索性就寫一個極簡單的程式，實際示範一下。

<%@ Page Language="C#" AutoEventWireup="true" %>

<html>

<head><title>UpdatePanel Call Javascript</title></head>

<body>

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

        <asp:UpdatePanel ID="UpdatePanel1" runat="server">

            <ContentTemplate>

                <asp:ScriptManager ID="ScriptManager1" runat="server">

                </asp:ScriptManager>

                <asp:Button ID="Button1" runat="server" Text="Button"

                onclick="Button1_Click" />

                <asp:HiddenField ID="hdnScript" runat="server" />

            </ContentTemplate>

        </asp:UpdatePanel>

        <script type="text/javascript">

        Sys.WebForms.PageRequestManager.getInstance().add_endRequest(blah);

        function blah() {

            eval($get("hdnScript").value);

        </script>

    </form>

<script type="text/C#" runat="server">

protected void Button1_Click(object sender, EventArgs e)

    hdnScript.Value = "alert('I did it!');";

</script>

</body>

</html>

運作的原理是利用add_endRequest()在每次UpdatePanel Postback時觸發blah()函數，blah()會用eval()執行Hidden欄位的字串值，所以在Server-Side將要執行的Javascript Code以字串方式傳回，按下按鈕後就會被執行。That's all, folks.

PS: 順便宣導一下資安觀念，傳回的Javascript Code不宜開放給User自行輸入或更動，不然會造成XSS攻擊的漏洞。
PS2: 用VS 2008寫這段Code時，輸入Sys.WebForms.PageRequestManager.getInstance()後還會提示add_Request，不亦快哉!!

Update 2007-12-08

Javascript牛人Ammon再露了一手，提供更簡便的做法ScriptManager.RegisterStartupScript()，在此謝過:

<%@ Page Language="C#" AutoEventWireup="true" %>

<html>

<head><title>UpdatePanel Call Javascript</title></head>

<body>

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

        <asp:ScriptManager ID="ScriptManager1" runat="server">

        </asp:ScriptManager>

        <asp:UpdatePanel ID="UpdatePanel1" runat="server">

            <ContentTemplate>

                <asp:Button ID="Button1" runat="server" Text="Button"

                onclick="Button1_Click" />

            </ContentTemplate>

        </asp:UpdatePanel>

    </form>

<script type="text/C#" runat="server">

protected void Button1_Click(object sender, EventArgs e)

    ScriptManager.RegisterStartupScript(Button1, typeof(Button),

        "alert", "alert('Amazing');", true);

</script>

</body>

</html>

Posted 08 December 2007 01:09 AM 由 Jeffrey | 4 comment(s)

Filed under: Tips, Javascript, ASP.NET, AJAX

Saturday, December 08, 2007 - 文章

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