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ASP.Net AJAX

ASP.Net AJAX. AJAX. Asynchronous JavaScript and XML : JavaScript, Document Object Model, Cascade Style Sheet, XML, server-side script such as .Net, etc. Partial refresh: It lets you update part of a web page without having to reload the entire page. RIA: Rich Internet Application

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ASP.Net AJAX

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  1. ASP.Net AJAX

  2. AJAX • Asynchronous JavaScript and XML: • JavaScript, Document Object Model, Cascade Style Sheet, XML, server-side script such as .Net, etc. • Partial refresh: It lets you update part of a web page without having to reload the entire page. • RIA: Rich Internet Application • Quick response time, interactive page

  3. How AJAX Updates a Page • When an event happens, JavaScript (AJAX engine) prepares a request and sends it to the web sever. • The server receives the request and processes it. • The server prepares a response and sends it back to the browser. • The JavaScript parses the response to update the page.

  4. ASP.Net AJAX Server Controls • ScriptManager: Enables the use of other AJAX controls. • UpdatePanel: A control that encloses standard ASP.net controls to be updated asynchronously (asynchronous postback) • Timer control: Trigger partial refresh at a set time interval.

  5. Creating Page with AJAX • 1. Add a ScriptManager control • 2. Add UpdatePanel control • 3. Add ASP.Net controls to the UpdatePanel

  6. Postback or Asynchronous PostBack • Page.IsPostBack • ScriptManager1.IsInAsyncPostBack

  7. Example 1: Two Counters

  8. Dim PostbackCounter, AsyncCounter As Integer Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Not Page.IsPostBack Then Session("PCounter") = PostbackCounter Session("Acounter") = AsyncCounter Else PostbackCounter = Session("PCounter") End If If ScriptManager1.IsInAsyncPostBack Then AsyncCounter = Session("Acounter") End If End Sub Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click PostbackCounter += 1 TextBox1.Text = PostbackCounter.ToString Session("PCounter") = PostbackCounter End Sub Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click AsyncCounter += 1 TextBox2.Text = AsyncCounter.ToString Session("Acounter") = AsyncCounter End Sub

  9. Example 2: Retrieve Customer Name

  10. Page.IsPostBack and ScriptManager1.IsInAsyncPostBack Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Not Page.IsPostBack Then TextBox3.Text = "First time" Else TextBox3.Text = "PostBack" End If If ScriptManager1.IsInAsyncPostBack Then TextBox2.Text = " IsAsyncPostBack" Else TextBox2.Text = " Not AsyncPostBack" End If End Sub

  11. Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\salesDB.mdb" Dim objConn As New OleDbConnection(strConn) Dim strSQL As String = "select * from customer where cid='" & TextBox1.Text & "';" Dim objComm As New OleDbCommand(strSQL, objConn) objConn.Open() Dim objDataReader As OleDbDataReader objDataReader = objComm.ExecuteReader() objDataReader.Read() TextBox2.Text = objDataReader("cname") objDataReader.Close() End Sub

  12. AJAX Timer • Add inside the UpdatePanel • Add Timer as a Trigger to the UpdatePanel • UpdateTriggers property • Timer’s interval and tick event

  13. Code Example Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles Timer1.Tick Label1.Text = DateTime.Now.ToLongTimeString() End Sub

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