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  • asp.net客户端回调

    在ASP.NET中要实现页面的部分回发，除了使用AJAX外还可以使用客户端回调。

    使用场景举例：一个很大的TreeView，初始化时只加载根节点，点击节点时加载子结点。

    以下是简单的示例代码：（要注意脚本安全验证）

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

    
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 
    
  1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"    >
    

    
    <html  >
    
    <head id="Head1" runat="server">
    
        <title>ASP.NET Example</title>
    
    <script type="text/javascript">    
    
        function ReceiveServerData(rValue)
    
        {
    
        Results.innerText     = rValue;
    
    }
    
      </script>
    
    </head>
    
    <body>
    
      <form id="form1" runat="server">
    
        <div>
    
          <asp:ListBox id="ListBox1" runat="server"></asp:ListBox>
    
          <br />
    
          <br />
    
          <button id="LookUpStockButton" onclick="LookUpStock()">Look Up Stock</button>
    
          <asp:LoginView id="LoginView1" runat="server">
    
          <LoggedInTemplate>
    
             <button id="LookUpSaleButton" onclick="LookUpSale()">Look Up Back Order</button>
    
          </LoggedInTemplate>
    
          </asp:LoginView>
    
          <br />
    
      Item status:     <span id="Results"></span>
    
        </div>
    
      </form>
    
    </body>
    
    </html>
    

    CodeBehind：
    using System;
    
    using System.Data;
    
    using System.Configuration;
    
    using System.Collections;
    
    using System.Web;
    
    using System.Web.Security;
    
    using System.Web.UI;
    
    using System.Web.UI.WebControls;
    
    using System.Web.UI.WebControls.WebParts;
    
    using System.Web.UI.HtmlControls;
    

    
    public partial class ClientCallback : System.Web.UI.Page,
    
     System.Web.UI.ICallbackEventHandler
    
    {
    
        protected System.Collections.Specialized.ListDictionary catalog;
    
        protected System.Collections.Specialized.ListDictionary saleitem;
    
        protected String returnValue;
    
        protected String validationLookUpStock = "LookUpStock";
    
        protected String validationLookUpSale = "LookUpSale";
    
        protected void Page_Load(object sender, EventArgs e)
    
        {
    
        Page.ClientScript.RegisterClientScriptBlock(    this.GetType(),
    
            validationLookUpStock,     "function LookUpStock() {  " +
    
                "var lb = document.forms[0].ListBox1; " +
    
                "var product = lb.options[lb.selectedIndex].text;  " +
    
                @"CallServer(product, ""LookUpStock"");}  ", true);
    
            if (User.Identity.IsAuthenticated)
    
            {
    
            Page.ClientScript.RegisterClientScriptBlock(    this.GetType(),
    
            validationLookUpSale,     "function LookUpSale() {  " +
    
                "var lb = document.forms[0].ListBox1; " +
    
                "var product = lb.options[lb.selectedIndex].text;  " +
    
                @"CallServer(product, ""LookUpSale"");} ", true);
    
        }
    

    
        String cbReference     = "var param = arg + '|' + context;" + 
    
            Page.ClientScript.GetCallbackEventReference(    this,
    
                "param", "ReceiveServerData", "context");
    
        String callbackScript;
    
        callbackScript     = "function CallServer(arg, context)" +
    
                "{ " + cbReference + "} ;";
    
        Page.ClientScript.RegisterClientScriptBlock(    this.GetType(),
    
                "CallServer", callbackScript, true);
    

    
        catalog     = new System.Collections.Specialized.ListDictionary();
    
        saleitem     = new System.Collections.Specialized.ListDictionary();
    
        catalog.Add(    "monitor", 12);
    
        catalog.Add(    "laptop", 10);
    
        catalog.Add(    "keyboard", 23);
    
        catalog.Add(    "mouse", 17);
    
        saleitem.Add(    "monitor", 1);
    
        saleitem.Add(    "laptop", 0);
    
        saleitem.Add(    "keyboard", 0);
    
        saleitem.Add(    "mouse", 1);
    

    
        ListBox1.DataSource     = catalog;
    
        ListBox1.DataTextField     = "key";
    
        ListBox1.DataBind();
    
    }
    
        public void RaiseCallbackEvent(String eventArgument)
    
        {
    
            string[] argParts = eventArgument.Split('|');
    
            if ((argParts == null) || (argParts.Length != 2))
    
            {
    
            returnValue     = "A problem occurred trying to retrieve stock count.";
    
                return;
    
        }
    
            string product = argParts[0];
    
            string validationaction = argParts[1];
    
            switch (validationaction)
    
            {
    
                case "LookUpStock":
    
                    try
    
                    {
    
                    Page.ClientScript.ValidateEvent(    "LookUpStockButton", validationaction);
    
                        if (catalog[product] == null)
    
                        {
    
                        returnValue     = "Item not found.";
    
                    }
    
                        else
    
                        {
    
                        returnValue     = catalog[product].ToString() + " in stock.";
    
                    }
    
                }
    
                    catch
    
                    {
    
                    returnValue     = "Can not retrieve stock count.";
    
                }     
    
                    break;
    
                case "LookUpSale":
    
                    try
    
                    {
    
                    Page.ClientScript.ValidateEvent(    "LookUpSaleButton", validationaction);
    
                        if (saleitem[product] == null)
    
                        {
    
                        returnValue     = "Item not found.";
    
                    }
    
                        else
    
                        {
    
                            if (Convert.ToBoolean(saleitem[product]))
    
                            returnValue     = "Item is on sale.";
    
                            else
    
                            returnValue     = "Item is not on sale.";
    
                    }
    
                }
    
                    catch
    
                    {
    
                    returnValue     = "Can not retrieve sale status.";
    
                }
    
                    break;
    
        }
    

    
    }
    
        public String GetCallbackResult()
    
        {
    
            return returnValue;
    
    }
    
        protected override void Render(HtmlTextWriter writer)
    
        {
    
        Page.ClientScript.RegisterForEventValidation(    "LookUpStockButton",
    
            validationLookUpStock);
    
            if (User.Identity.IsAuthenticated)
    
            {
    
            Page.ClientScript.RegisterForEventValidation(    "LookUpSaleButton",
    
                validationLookUpSale);
    
        }
    
            base.Render(writer);
    
    }
    
}
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  • 原文地址：https://www.cnblogs.com/guojin705/p/1205532.html
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