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<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="RandomNumber" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Callback Page</title>
<script type="text/javascript">
function GetNumber(){
UseCallback();
}
function GetRandomNumberFromServer(TextBox1, context){
document.forms[0].TextBox1.value = TextBox1;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<input id="Button1"
type="button"
value="Get Random Number"
onclick="GetNumber()" />
<br />
<br />
<asp:TextBox ID="TextBox1" Runat="server"></asp:TextBox>
</div>
</form>
</body>
</html>
File: Default.aspx.vb
Partial Class RandomNumber
Inherits System.Web.UI.Page
Implements System.Web.UI.ICallbackEventHandler
Dim _callbackResult As String = Nothing
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles Me.Load
Dim cbReference As String = Page.ClientScript.GetCallbackEventReference(Me, "arg", "GetRandomNumberFromServer", "context")
Dim cbScript As String = "function UseCallback(arg, context)" & _
"{" & cbReference & ";" & "}"
Page.ClientScript.RegisterClientScriptBlock(Me.GetType(), _
"UseCallback", cbScript, True)
End Sub
Public Sub RaiseCallbackEvent(ByVal eventArgument As String) Implements System.Web.UI.ICallbackEventHandler.RaiseCallbackEvent
_callbackResult = Rnd().ToString()
End Sub
Public Function GetCallbackResult() As String Implements System.Web.UI.ICallbackEventHandler.GetCallbackResult
Return _callbackResult
End Function
End Class
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