最近在做一個項目，有一個頁面用到異步刷新，因爲不想用updatepanel處理，就想到了.net自帶的ICallbackEventHandler接口，在這裏簡單的對照msdn寫了一個列子。
既然要異步，那麼肯定要手動在前臺寫部分js了，既然是交互，那麼傳值這一步是少不了的了，顯然首先要有一個調取的頁面元素值得方法
- function LookUpStock() {
- var lb = document.getElementById("ListBox1");
- var product = lb.options[lb.selectedIndex].text;
- CallServer(product, "");
- }
那麼既然是異步更新數據，那麼修改後的值肯定是js進行操作的了，這裏就添加了一個返回值的js方法
- function ReceiveServerData(rValue) {
- document.getElementById("ResultsSpan").innerHTML = rValue;
- }
前臺頁面的html內容如下：
- <html xmlns="http://www.w3.org/1999/xhtml" >
- <head id="Head1" runat="server">
- <title>Client Callback Example</title>
- <script type="text/ecmascript">
- function LookUpStock() {
- var lb = document.getElementById("ListBox1");
- var product = lb.options[lb.selectedIndex].text;
- CallServer(product, "");
- }
- function ReceiveServerData(rValue) {
- document.getElementById("ResultsSpan").innerHTML = rValue;
- }
- </script>
- </head>
- <body>
- <form id="form1" runat="server">
- <div>
- <asp:ListBox ID="ListBox1" Runat="server"></asp:ListBox>
- <br />
- <br />
- <button type="Button" onclick="LookUpStock()">Look Up Stock</button>
- <br />
- <br />
- Items in stock: <span id="ResultsSpan" runat="server"></span>
- <br />
- </div>
- </form>
- </body>
- </html>
在後臺：
- public partial class Default2 : System.Web.UI.Page,System.Web.UI.ICallbackEventHandler
- {
- protected System.Collections.Specialized.ListDictionary catalog;
- protected String returnValue;//用來得到返回值
- protected void Page_Load(object sender, EventArgs e)
- {
- String cbReference =
- Page.ClientScript.GetCallbackEventReference(this,
- "arg", "ReceiveServerData", "context");//添加頁面回傳觸發操作
- String callbackScript;
- callbackScript = "function CallServer(arg, context)" +
- "{ " + cbReference + ";}";
- Page.ClientScript.RegisterClientScriptBlock(this.GetType(),
- "CallServer", callbackScript, true);
- //註冊前臺CallServer方法，方法內容就是 callbackScript
- catalog = new System.Collections.Specialized.ListDictionary();
- catalog.Add("monitor", 12);
- catalog.Add("laptop", 10);
- catalog.Add("keyboard", 23);
- catalog.Add("mouse", 17);
- ListBox1.DataSource = catalog;
- ListBox1.DataTextField = "key";
- ListBox1.DataBind();
- }
- //這裏是繼承自ICallbackEventHandler的方法，將頁面的值傳入處理
- public void RaiseCallbackEvent(String eventArgument)
- {
- if (catalog[eventArgument] == null)
- {
- returnValue = "-1";
- }
- else
- {
- returnValue = catalog[eventArgument].ToString();
- }
- }
- //這裏是繼承自ICallbackEventHandler的方法
- //將處理後的值返回，供頁面使用
- public String GetCallbackResult()
- {
- return returnValue;
- }
- }