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Posted 6 Jul 2007

Events Between Web Forms

, 6 Jul 2007
Raise Events Between Web Forms Using CallBacks or Ajax
Imports System.IO

Partial Public Class _Default
    Inherits System.Web.UI.Page
    Implements System.Web.UI.ICallbackEventHandler

    ''' <summary>
    ''' Holds the result that will be send to the Page
    ''' </summary>
    Protected CallBackResult As String

    ''' <summary>
    ''' Register propper callbacks
    ''' </summary>
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        'Register the method that receives the call back result
        Dim ReceiverCallBackMethod As String
        ReceiverCallBackMethod = Page.ClientScript.GetCallbackEventReference(Me, "arg", "ReceiveCallBackResult", "context")
        'Register the method that makes the callback call
        Dim callbackMethod As String
        callbackMethod = "function CallServer(arg, context) { " & ReceiverCallBackMethod & "} ;"
        Page.ClientScript.RegisterClientScriptBlock(Me.GetType(), "CallServer", callbackMethod, True)

    End Sub

    ''' <summary>
    ''' Creates HTML code 
    ''' </summary>
    ''' <returns>The HTML</returns>
    Public Function ShowTheData() As String

        'The data source
        Dim DS As New DataSet
        'Check if the file exists
        Dim file As New FileInfo(Server.MapPath(Request.ApplicationPath) & "/Data.xml")
        If Not file.Exists Then
            DS.Tables("Users").Columns.Add("User Name", GetType(String))
            DS.Tables("Users").Columns.Add("Age", GetType(Integer))
            DS.WriteXml(file.FullName, XmlWriteMode.WriteSchema)
        End If

        'The HTML
        Dim HTML As String = "<Table border=1>"
        'Add the headers
        HTML &= "<tr><td>Name</td><td>Age</td></tr>"

        'Create the Rows
        For Each Row As DataRow In DS.Tables("Users").Rows
            Dim TR As String = "<tr>"
            'show the name and Age
            TR &= "<td>" & Row(0).ToString & "</td>"
            TR &= "<td>" & Row(1).ToString & "</td>"
            TR &= "</tr>"
            HTML &= TR

        Return HTML & "</Table>"
    End Function

    ''' <summary>
    ''' The Event that proccess the Call Back
    ''' </summary>
    ''' <param name="eventArgument">Send values to proccess here</param>
    Public Sub RaiseCallbackEvent(ByVal eventArgument As String) _
    Implements System.Web.UI.ICallbackEventHandler.RaiseCallbackEvent

        'In this case we dont need to proccess nothing 

    End Sub

    ''' <summary>
    ''' This will return some data to the Caller Page
    ''' </summary>
    ''' <returns>HTML string with all the users</returns>
    Public Function GetCallbackResult() _
    As String Implements _

        'return the value
        Return ShowTheData()

    End Function

End Class

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About the Author

Web Developer
Mexico Mexico
I am Pedro Ramirez from mexico, work for, the company is located in Mexico, we do outsourcing and nearshore development, we are focused on SaaS nearshore development, I started with VB.Net, but now I am ambidextrous using VB.Net or C#.

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