页面开发技巧 asp.net控件事件以维持滚动位置客户端回调

1、提交后的回发时能自动进入上次的当前位置

例如，如果数据项导致大型页回发，则最终用户需要将页滚动到此前正在编辑它们的位置，才能继续。页开发人员通过以下方法可以简单地标记窗体，以维持滚动位置：在 @Page 指令中将 MaintainScrollPositionOnPostBack 属性设置为 true，或在 Web.config 中进行此设置，以应用于应用程序中的所有页。

2、Button 控件的 OnClientClick 属性允许您在此按钮被单击时以编程方式运行客户端脚本。该按钮呈现客户端 onclick 属性以及按钮自身的 Javascript。

3、用于控件的一个令人惊喜的新功能是“客户端回调”，该功能允许控件向服务器执行带外请求以获取附加数据，而不发送整页。此功能依赖于用于回调处理（通常通过 XMLHTTP）的浏览器支持，该支持由 SupportsClientCallbacks 在浏览器功能中指定。

其实一般的无刷新页面就可以使用客户端回调来实现，只有复杂的才需要使用AJAX等

<%@ Page Language="C#" AutoEventWireup="true" EnableEventValidation="false" CodeFile="CallBackEventHandler_cs.aspx.cs" Inherits="CallBackEventHandler_cs" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<title>Client CallBack</title>

</head>

<body>

<h3>Cascading DropDownLists Using ICallBackEventHandler</h3>

<asp:DropDownList ID="ParentDropDown"

onchange="GetChildren(this.options[this.selectedIndex].value, 'ddl');"

Runat="server">

<asp:ListItem Text="Item 1" />

<asp:ListItem Text="Item 2" />

<asp:ListItem Text="Item 3" />

</asp:DropDownList>

<asp:DropDownList ID="ChildDropDown" AutoPostBack="true" style="visibility:hidden" Runat="Server">

<asp:ListItem Text="Child Item" />

</asp:DropDownList>

<asp:Label ID="Label1" runat="server"/>

function ClientCallback(result, context){

var childDropDown = document.forms[0].elements['<%=ChildDropDown.UniqueID%>'];

if (!childDropDown){

return;

}

childDropDown.length = 0;

if (!result){

return;

}

var rows = result.split('|');

for (var i = 0; i < rows.length; ++i){

var option = document.createElement("OPTION");

option.value = rows[i];

option.innerHTML = rows[i];

childDropDown.appendChild(option);

}

childDropDown.style.visibility = "visible";

}

function ClientCallbackError(result, context){

alert(result);

}

</script>

</form>

</body>

</html>

//----------------------------------------------------------------------- // This file is part of the Microsoft .NET SDK Code Samples. // // Copyright (C) Microsoft Corporation. All rights reserved. // //This source code is intended only as a supplement to Microsoft //Development Tools and/or on-line documentation. See these other //materials for detailed information regarding Microsoft code samples. // //THIS CODE AND INFORMATION ARE PROVIDED AS IS WITHOUT WARRANTY OF ANY //KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE //IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A //PARTICULAR PURPOSE. //----------------------------------------------------------------------- using System; using System.Web.UI; public partial class CallBackEventHandler_cs : System.Web.UI.Page, ICallbackEventHandler { private string _callbackResult; private void Page_Load(object source, EventArgs e) { String callBack = Page.ClientScript.GetCallbackEventReference(this, "arg", "ClientCallback", "context", "ClientCallbackError", false); String clientFunction = "function GetChildren(arg, context){ " + callBack + "; }"; Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "GetChildren", clientFunction, true); if (Page.IsPostBack && !Page.IsCallback) { Label1.Text = "You Selected: " + Request.Form["ParentDropDown"] + ": " + Request.Form["ChildDropDown"]; } } public string GetCallbackResult() { return _callbackResult; } public void RaiseCallbackEvent(string eventArgument) { switch (eventArgument) { case "Item 1": _callbackResult = "One|Two|Three"; break; case "Item 2": _callbackResult = "Four|Five|Six"; break; case "Item 3": _callbackResult = "Seven|Eight|Nine"; break; default: _callbackResult = ""; break; } } }

source http://www.cnblogs.com/firstyi/archive/2006/11/13/559156.html

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