How to add Control dynamically in an ASP.NET AJAX application

Most of us know how to create controls dynamically in an ASP.NET application. However a lot of users get confused while creating controls dynamically in an ASP.NET AJAX application. This is as the there is an async postback involved. Here's a very common technique to create controls dynamically in an ASP.NET AJAX application using ViewState


<body>


    <form id="form1" runat="server">


    <div>


    <asp:ScriptManager ID="ScriptManager1" runat="server">


    </asp:ScriptManager>


    <asp:UpdatePanel ID="UpdatePanel1" runat="server">


    <ContentTemplate>


           <asp:Button ID="Button1" runat="server" Text="Create TextBoxes" onclick="Button1_Click" />


   </ContentTemplate>


   </asp:UpdatePanel>


    </div>


    </form>


</body>




C#


    protected void Button1_Click(object sender, EventArgs e)


    {


        int cnt = 0;


 


        if (ViewState["txtBoxes"] != null)


            cnt = (int)ViewState["txtBoxes"];


 


        cnt = cnt + 1;


        ViewState["txtBoxes"] = cnt;


 


 


        for (int i = 0; i < cnt; i++)


        {


            TextBox tb = new TextBox();


            tb.Text = "";


            tb.ID = "TextBox" + cnt;


            UpdatePanel1.ContentTemplateContainer.Controls.Add(tb);


        }    


    }




VB.NET


    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)


        Dim cnt As Integer = 0


 


        If ViewState("txtBoxes") IsNot Nothing Then


            cnt = CInt(Fix(ViewState("txtBoxes")))


        End If


 


        cnt = cnt + 1


        ViewState("txtBoxes") = cnt


 


 


        For i As Integer = 0 To cnt - 1


            Dim tb As New TextBox()


            tb.Text = ""


            tb.ID = "TextBox" & cnt


            UpdatePanel1.ContentTemplateContainer.Controls.Add(tb)


        Next i


    End Sub




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About The Author

Suprotim Agarwal
Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

Follow him on twitter @suprotimagarwal.

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