PerformCallback

实现客户端，服务端异步通信的。

从客户端到服务端的通信：PerformCallback()。PerformCallback就是从客户端到服务端的桥梁，它是单向的只能从客户端发起到服务端。在Perform Callback()括号当中我们可以传递一些参数到服务器端，从而达到更新效果。服务器端的接受并异步刷新：Callback()。当从服务端PerformCallback唤醒以后，响应的控件Callback事件开始执行(控件的服务器事件中可以找到)。

并且通过Parameter键值来获取从客户端传过来的值进行相关的处理。 客户端：Code

<html xmlns="http://www.w3.org/1999/xhtml">

<head runat="server">

<title>PerTest</title>

<script language="javascript" type="text/javascript">

//客户端处理下拉框选择项改变事件,client端aspxcombox下拉框改变事件为SelectedIndexChanged

function OnEmployeesChanged(s){

//PerformCallback事件实际上时dev系列控件客户端服务器端异步通信的"大使"，通过PerfromCallback事件

//将客户端的通信要求传递给服务端,在服务端通过控件的callback事件来接受相关参数并进行页面异步刷新

devcbxChi.PerformCallback(s.GetValue());

}

</script>

</head>

<body>

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

<div>

<dxe:ASPxComboBox runat="server" ID="devcbxPar2" DropDownStyle="DropDownList" EnableIncrementalFiltering="True"

EnableSynchronization="False" ClientInstanceName="devcbxPar2"

Width="160px">

<ClientSideEvents SelectedIndexChanged="function(s, e) { OnEmployeesChanged(s); }"></ClientSideEvents>

</dxe:ASPxComboBox>

<dxe:ASPxComboBox runat="server" ID="devcbxChi" DropDownStyle="DropDownList" EnableIncrementalFiltering="True"

EnableSynchronization="False" ClientInstanceName="devcbxChi"

Width="160px" oncallback="devcbxChi_Callback">

</dxe:ASPxComboBox>

</div>

</form>

</body>

</html>

using DevExpress.Web.ASPxEditors;

Code

SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["northwind"].ConnectionString);

protected void Page_Load(object sender, EventArgs e)

{

if (!IsPostBack)

{

devcbxPar2.Items.Clear();

string selectSQL = "select EmployeeID,FirstName from Employees";

SqlDataAdapter SDA = new SqlDataAdapter(selectSQL, conn);

DataSet DS = new DataSet();

SDA.Fill(DS);

for (int i = 0; i < DS.Tables[0].Rows.Count; i++)

{

devcbxPar2.Items.Add(new ListEditItem(DS.Tables[0].Rows[i]["FirstName"].ToString().Trim(), DS.Tables[0].Rows[i]["EmployeeID"] .ToString().Trim()));

}

}

}     protected void devcbxChi_Callback(object source, DevExpress.Web.ASPxClasses.CallbackEventArgsBase e)

{

//得到从客户端传递过来的参数来进行异步通信响应

string parm = e.Parameter.Trim();

string selectSQL = "select TerritoryID from EmployeeTerritories where EmployeeID='" + parm + "'";

SqlDataAdapter SDA = new SqlDataAdapter(selectSQL, conn);

DataSet DS = new DataSet();

SDA.Fill(DS);

devcbxChi.Items.Clear();

for (int i = 0; i < DS.Tables[0].Rows.Count; i++)

{

devcbxChi.Items.Add(DS.Tables[0].Rows[i]["TerritoryID"].ToString().Trim());

}

devcbxChi.SelectedIndex = 0;     }

原文地址：http://blog.csdn.net/xueer8835/article/details/6018969