FAQ - Frequently Asked Questions

Re: dynamic control help plzzzzzzzzzzzzzzz.....

mausimo — Thu, 05 Nov 2009 17:36:37 GMT

For everyone that wanted viewstate code in C#....

const bool CREATE_SELECTED = true;
    const bool VIEW_SELECTED = true;
    const bool CURRENT_SELECTED = true;

    //store property value in viewstate so that it will survive postbacks
     private bool p_Create
     {
         set
         {
            ViewState["CREATE_SELECTED"] = value;
         }
         get
         {
            return Convert.ToBoolean(ViewState["CREATE_SELECTED"]);
         }
      }

     private bool p_View
     {
         set
         {
             ViewState["VIEW_SELECTED"] = value;
         }
         get
         {
             return Convert.ToBoolean(ViewState["VIEW_SELECTED"]);
         }
     }

     private bool p_Current
     {
         set
         {
             ViewState["CURRENT_SELECTED"] = value;
         }
         get
         {
             return Convert.ToBoolean(ViewState["CURRENT_SELECTED"]);
         }
     }

 protected void Page_Load(object sender, EventArgs e)
    {
        if (p_Create)
        {
            this.CreateWasClicked();
        }
        if (p_View)
        {
            this.ViewWasClicked();
        }
        if (p_Current)
        {
            this.CurrentWasClicked();
        }       
    }

    /// <summary>
    /// button used to view the view Articles
    /// </summary>
    protected void btnView_Click(object sender, EventArgs e)
    {
        //if the add article interface is already visible then hide it
        if (PlaceHolder_View.Visible == true)
        {
            PlaceHolder_View.Visible = false;
            btnView.Text = "View";

            //VERY IMPORTANT -> remember that we created these controls for the next postback
            this.p_View = false;
        }
        //if the add article interface is not visible then show it
        else
        {
            //displaying the add/create arcticle interface
            PlaceHolder_View.Visible = true;
            //changing button text to hide the create article interface.
            btnView.Text = "Hide View";

            //VERY IMPORTANT -> remember that we created these controls for the next postback
            this.p_View = true;
        }
    }

    /// <summary>
    /// for keeping view visible after post back if it was clicked
    /// </summary>
    protected void ViewWasClicked()
    {
        PlaceHolder_View.Visible = true;
    }

This is the jist of using viewsates to keep post back variables in C#. This is from my code, it is showing you how to use the functionality. Manipulate this how you want, you can use any type (does not have to be bool etc).

Good-Luck

-Mike

Re: dynamic control help plzzzzzzzzzzzzzzz.....

girish dagdiya — Thu, 29 Oct 2009 05:11:44 GMT

hi,

you have written -- having error with find control part

but where is the code for finding control.

Re: dynamic control help plzzzzzzzzzzzzzzz.....

prakashshamala — Wed, 28 Oct 2009 09:07:37 GMT

amitha:
this is my program logic

i am new to this web developement so looking forward for your help

plzzzzzzzzzz go thru

reply asap

having error with find control part

do suggest all changes nedeed

or else

if possible can u modify my code n send rest of my project is going good i am really stuck with this plzz

i hav to take values frm text box n calculate base on it

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

<asp:Panel id="pnlone" runat="server" Height="74px" Width="384px">

<asp:Label ID="lblAmnt" Text=" Enter the pension amount:" runat="server" Width="180px"></asp:Label>

<asp:TextBox id="tbAmnt" runat="server"/><br />

<asp:Label ID="lblNo" Text=" Enter the number of persons:" runat="server" Width="180px"></asp:Label>

<asp:TextBox id="tbNo" runat="server"/><br />

<center> <asp:button id="Enter" text="Enter" OnClick="SubmitBtn_Click" runat="server"/></center><br />

<p><asp:PlaceHolder id="Area1" runat="server"></asp:PlaceHolder></p>

<table id="tblReslt" runat="server">

<tr>

<td id="col1" runat="server"></td>

<td id="col2" runat="server"></td>

</tr>

<tr>

<td><asp:Button ID="submit" runat="server" visible="false" OnClick="calInheritAmnt" Text="submit" /></td>

</tr>

</table>

</asp:Panel>

<asp:table id="tblInheritDetails" runat="server" width="100%"/>

</form>

Partial Class testajax
Inherits System.Web.UI.Page
Sub Page_Load(ByVal Sender As Object, ByVal E As EventArgs)
If IsPostBack Then

SubmitBtn_Click(Sender, E)

End If

End Sub
Public Sub SubmitBtn_Click(ByVal Sender As Object, ByVal E As EventArgs)
Dim I As Integer
For I = 1 To CInt(tbNo.Text.Trim())
Dim tbInhrtrName As New TextBox
tbInhrtrName.ID = "tbDynamic" & I.ToStringtbInhrtrName.Text = "Control" & I
Form.Controls.Add(tbInhrtrName)

'Area1.Controls.Add(tbInhrtrName)
Dim MyLiteral = New LiteralControl
MyLiteral.Text = "<BR><BR>"

Form.Controls.Add(MyLiteral)

'Area1.Controls.Add(MyLiteral)

Next

submit.Visible = "true"

tblInheritDetails.Visible = "true"

End Sub
Protected Sub calInheritAmnt(ByVal sender As Object, ByVal e As System.EventArgs) Handles submit.Click
Dim id As String

Dim I As Integer

'Dim tb As New TextBox
For I = 1 To CInt(tbNo.Text.Trim())
Dim tb As New TextBox
id = "tbDynamic" & I.ToStringtb = DirectCast(sender, TextBox)
Response.Write(tb.Text.ToString())

'Response.Write(Session(id) & "<br/>")

Next

End Sub

End Class

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

rlnd — Sun, 25 Oct 2009 18:05:12 GMT

Is it possible that this approach doesn't work for custom events? I've got a ul to which I'm programmatically adding (ASP.net user control) lis. I'm re-adding these user controls in the Page_Load event and 'ordinary' events (that is: LinkButton.Clicks) work fine - only my custom events somehow lose their handlers during the postback.

Here is how I'm adding the controls to the list (the IDs are persistent over postbacks):

Newsletter_TextPart control = (Newsletter_TextPart)LoadControl("~/Newsletter/TextPart.ascx");
        control.ID = "part_" + value.PartID;


        control.Deleted += new Newsletter_TextPart.DeletedEventHandler(part_Deleted);

        AsyncPostBackTrigger t2 = new AsyncPostBackTrigger();
        t2.ControlID = control.ID;
        t2.EventName = "Deleted";

        upnlText.Triggers.Add(t2);


        ulTextParts.Controls.Add(control);
        control.Part = value;

Here is the relevant code in the UserControl:

    public delegate void DeletedEventHandler(object sender, PartEventArgs e);

    public event DeletedEventHandler Deleted;

    protected void lbtDelete_Click(object sender, EventArgs e)
    {
        if (Deleted != null)
            Deleted(this, new PartEventArgs(Part)); //'Part' is a property of the control
    }

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

batool — Wed, 14 Oct 2009 19:51:27 GMT

miteshsura:
try this link .. http://www.developerfusion.com/tools/convert/vb-to-csharp/

I have already tried this site... I got some problems in the "DynamicControlSelection" Method

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

miteshsura — Wed, 14 Oct 2009 16:47:54 GMT

try this link .. http://www.developerfusion.com/tools/convert/vb-to-csharp/

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

batool — Wed, 14 Oct 2009 08:22:39 GMT

I tried to convert this code to C#, but its not working... Can anybody convert it?

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

girish dagdiya — Thu, 08 Oct 2009 06:30:15 GMT

hi,

nice article.But i have different problem here.

I am creating one tabcontainer and 13 tabpanels dynamically in page_init.I have also created iframe in each tabpanel dynamically in page_init.Now how can i access first iframe's id.I am getting only last iframe's id once page loads.

The mypage.aspx.cs code is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using AjaxControlToolkit;
using System.Configuration;

public partial class Courses : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
    SqlConnection conWeb = new SqlConnection(ConfigurationManager.ConnectionStrings["MainConnectionString"].ConnectionString);
    protected UpdatePanel upanel, MainPanel;
    public TabContainer MainTabcontainer, tabcontainer;
    public TabPanel tabpanel;
    public System.Web.UI.HtmlControls.HtmlGenericControl frame;
    public Label lblpage=new Label();
    int counter = 0;

    protected void Page_Load(object sender, EventArgs e)
    {
        Label myLable, myLable1;
        myLable = (Label)Master.FindControl("Label1");
        myLable.Text = "Courses ";
        myLable1 = (Label)Master.FindControl("Label2");
        myLable1.Text = "";

    }
    protected void Page_Init(object sender, EventArgs e)
    {
        Label myLable, myLable1;
        myLable = (Label)Master.FindControl("Label1");
        myLable.Text = "";
        myLable1 = (Label)Master.FindControl("Label2");
        myLable1.Text = "";

        funShowData();
    }
    public void funShowData()
    {

        SqlCommand cmd = new SqlCommand("SELECT query to access ids", con);
        con.Open();
        SqlDataReader sdr = cmd.ExecuteReader();
        int i = 0;

        MainPanel = new UpdatePanel();
        MainTabcontainer = new TabContainer();
        MainTabcontainer.Width = 660;

        while (sdr.Read())
        {

            tabpanel = new TabPanel();
            tabpanel.ID = "tab" + i.ToString();
            tabpanel.EnableViewState = true;
            tabpanel.HeaderText = sdr[1].ToString();
            tabpanel.Enabled = true;

            string val = sdr[0].ToString();
            if (val.Length == 1)
            {
                val = "0" + val;
            }

tabpanel.TabIndex = Convert.ToSByte(val);
upanel = new UpdatePanel();

upanel.ID = "upanel";
tabcontainer = new TabContainer();

tabcontainer.EnableViewState = true;

            upanel.ContentTemplateContainer.Controls.Add(tabcontainer);
            tabpanel.Controls.Add(upanel);

            frame = new System.Web.UI.HtmlControls.HtmlGenericControl("iframe");
            frame.ID = "frame"+counter;
            frame.EnableViewState = true;
            frame.Attributes.Add("frameborder", "0");
            frame.Attributes.Add("src","Tabs/pr_tab.aspx");
            frame.Attributes.Add("width", "630px");
            frame.Attributes.Add("height", "385px");
            tabpanel.Controls.Add(frame);

            Label1.Text = "Counter "+counter;
            MainTabcontainer.Tabs.Add(tabpanel);
            i++; counter++;

        }
        sdr.Close();
        con.Close();
        MainPanel.ContentTemplateContainer.Controls.Add(MainTabcontainer);
        div1.Controls.Add(MainPanel);
    }
    protected void ImageButton_download_Click(object sender, ImageClickEventArgs e)
    {

        if (MainTabcontainer.ActiveTabIndex == 0)
        {
            Label myLable, myLable1;
            myLable = (Label)Master.FindControl("Label1");
            myLable.Text = "Course > ";
            myLable1 = (Label)Master.FindControl("Label2");
            myLable1.Text = "DVLSI > e-brochure ";

ScriptManager.RegisterStartupScript(Page, this.GetType(), "getfun", "javascript:getfun(" + MainTabcontainer.ActiveTabIndex + ");", true);//To register client script

        }
    }

}

mypage.aspx:

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

alert(frame.id);
   }
   </script>

    <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
    <div id="div2" runat="server" style="float:left">
        <table>
        <tr>
            <td style="border: 1px solid #3399FF; height: 435px; width: 70px; "
                valign="top">
                <br />
                <br />
                <asp:ImageButton ID="ImageButton_download" runat="server" ImageUrl="~/Images/arrows.gif"
                    OnClick="ImageButton_download_Click" />
                <br />
                <br />

            </td>
        </tr>
    </table>
</div>
    <div id="div1" runat="server" style="float:right">




    </div>

</asp:Content>

In function getfun(index),how can i access first tabpanels iframe.

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

dch3 — Tue, 29 Sep 2009 18:58:53 GMT

From personal experience, I nearly killed myself over trying to sort out problems that I had with adding ListItems to a Drop Down List in a repeater. The code seemed to work perfectly fine outside of the repeater with the ListItems being persisted and the _SelectedIndexChanged event being raised and other what not. I finally figured out that instead of having the Drop Down List in the markup and adding the ListItems to it, that I needed to just have an asp : placeholder in the content and the create the entire Drop Down List from start to finish in the code behind via the _ItemDataBound event. I had checked everything including EnableViewState on the control, on the Repeater on the Page.

Of course now that its working, the whole thing has to be scrapped given that I didn't factor in how the number of items in the repeater and the Drop Down List would impact the load time of the page

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

rgenco1 — Thu, 17 Sep 2009 16:05:50 GMT

Hi all,

i use the example to adding N number of dynamic controls to a page . I want to create dropdownlist populate by Dataset and in cmdProcessControls_Click I wanto to show the item choise by user in dropdownlist but I don't get the same behaviour. When Click in cmdProcessControls button i view dropdownlist without item and label control empty. If I use dropdownlist populate by listitems It works.

    private int StepCounter
    {
        get
        {
            object o1 = ViewState["StepCounter"];
            if (o1 == null) return 0;
            return (int)o1;
        }
        set { ViewState["StepCounter"] = value; }
    }

    void Page_PreRender()
    {
        cmdProcessControls.Enabled = StepCounter > 0;
    }

    protected void Page_Load(object sender, EventArgs e) 
    { 
        //recreate dynamic controls on all postback by page_load at the latest 
        //we use page_load instead of init so that we can access viewstate. 
        if (Page.IsPostBack)
        {
            for (int j = 1; j <= StepCounter; j++)
            {
                DropDownList ddltest = new DropDownList();
                ddltest.ID = "ddltest" + j;
                //ddltest.AutoPostBack = false;
                Label lblDomanda = new Label();
                lblDomanda.ID = "lblD" + j;
                Label lblTest = new Label();
                lblTest.ID = "lbl" + j;
                this.PlaceHolder1.Controls.Add(lblDomanda);
                this.PlaceHolder1.Controls.Add(lblTest);
                this.PlaceHolder1.Controls.Add(ddltest);
            }

        }
        else
        {
            Label lblTest = new Label();
            lblTest.Text = "Inizio Procedura Guidata. Clicca su Add Domanda per Proseguire";
            this.PlaceHolder1.Controls.Add(lblTest);
        }

    } 


    protected void cmdProcessControls_Click(object sender, EventArgs e) 
    { 
        

        string tipoControl = string.Empty;
        foreach (Control ddl in this.PlaceHolder1.Controls)
        {
            tipoControl = ddl.GetType().ToString();
            if ( tipoControl == "System.Web.UI.WebControls.DropDownList")
                Response.Write(string.Format("Control ID: {0}, Text: {1} <br/>", ((DropDownList)ddl).ID, ((DropDownList)ddl).SelectedValue));
            else if (tipoControl == "System.Web.UI.WebControls.Label")
                Response.Write(string.Format("LABEL ID: {0}, Text: {1} <br/>", ((Label)ddl).ID, ((Label)ddl).Text));
        }

    }

    protected void cmdAddTextbox_Click(object sender, EventArgs e)
    {
        string prova = string.Empty;
        SqlDataAdapter sdaDomande;
        SqlDataAdapter sdaRisposte;
        string constr = ConfigurationManager.ConnectionStrings["ProteoConnectionString"].ConnectionString;
        SqlConnection connection = new SqlConnection(constr);
        if (StepCounter == 0)
        {
            sdaDomande = new SqlDataAdapter("SELECT ID_Domanda, Testo, ID_Domanda_Padre, Valore FROM Domande WHERE ID_Domanda = ID_Domanda_Padre ORDER BY ID_Domanda", connection);
        }
        else
        {
            sdaDomande = new SqlDataAdapter("SELECT ID_Domanda, Testo, ID_Domanda_Padre, Valore FROM Domande WHERE ID_Domanda = @ID_Domanda_Padre ORDER BY ID_Domanda", connection);
        }
        DataSet ds = new DataSet();
        sdaDomande.Fill(ds, "Domande");
        //prova = "D" + ds.Tables["Domande"].Rows[0]["ID_Domanda"].ToString() + "-" + ds.Tables["Domande"].Rows[0]["Testo"].ToString();
        sdaRisposte = new SqlDataAdapter("SELECT * FROM Risposte WHERE ID_Domanda = @ID_Domanda ORDER BY ID_Risposta, ID_Domanda", connection);
        DataSet dsRisp = new DataSet();
        
        //increment counter 
        StepCounter += 1;
        for (int i = 0; i <= ds.Tables["Domande"].Rows.Count - 1; i++)
        {
            prova = ds.Tables["Domande"].Rows[i]["ID_Domanda"].ToString();
            sdaRisposte.SelectCommand.Parameters.Add("@ID_Domanda", SqlDbType.Int).Value = prova;
            sdaRisposte.Fill(dsRisp, "Risposte");

            //add new dynamic control

            DropDownList ddltest = new DropDownList();
            ddltest.DataSource = dsRisp;
            ddltest.ID = "ddltest" + StepCounter;
            ddltest.AutoPostBack = false;
            ddltest.DataTextField = "Testo";
            ddltest.DataValueField = "ID_Risposta";
            ddltest.DataBind();
            Label lblDomanda = new Label();
            lblDomanda.Text = "D" + ds.Tables["Domande"].Rows[i]["ID_Domanda"].ToString() + "-" + ds.Tables["Domande"].Rows[i]["Testo"].ToString();
            lblDomanda.ID = "lblD" + StepCounter;
            Label lblTest = new Label();
            lblTest.Text = "Seleziona Risposta";
            lblTest.ID = "lbl" + StepCounter;
            this.PlaceHolder1.Controls.Add(lblDomanda);
            this.PlaceHolder1.Controls.Add(lblTest);
            this.PlaceHolder1.Controls.Add(ddltest);
        }
    }

<head id="Head1" runat="server">
    <style type="text/css">
        html
        {
            font:14px Georgia,Serif;
        }
        fieldset
        {
            display:block;
            width:600px;
            padding:20px;
            margin:10px;
        }
    </style>
    <title>Wizard</title>
</head>
<body>
    <form id="form1" runat="server">  
    <div>  
       <%-- <asp:Button ID="cmdProcessControls" runat="server" Text="Fine" 
            onclick="cmdProcessControls_Click" /> --%> 
        <%--<asp:Button ID="cmdAddTextbox" runat="server" Text="Add domande" onclick="cmdAddTextbox_Click" 
             /> --%> 
        
     
            <asp:Label id="lblStepNumber" Runat="server" />

            <fieldset>
            <legend><asp:Literal ID="ltlStep" runat="server" /></legend>
            <asp:PlaceHolder ID="PlaceHolder1" runat="server" />
            </fieldset>

    <asp:Button 
        ID="cmdProcessControls" runat="server" onclick="cmdProcessControls_Click"
        Text="< Fine"
        CausesValidation="false"/>
    
    <asp:Button
            ID="cmdAddTextbox" runat="server" onclick="cmdAddTextbox_Click" 
        Text="Add domande >" />

    </div>
</form> 
</body>

I try to reply the idcontrols how explain in your post but my code don't work like I want.

Any ideas to help me?

Thanks,

Roberto

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

dhinakaranpc — Tue, 11 Aug 2009 03:40:19 GMT

Ya its a good article .Very useful for the begginers to know about the Dynamic controls.

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

amitkumartiwari29 — Tue, 04 Aug 2009 11:37:38 GMT

Thank you guys, I was looking for the perfect solution from a long time. This article helped me a lot. Thanks :-)

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

miteshsura — Fri, 17 Jul 2009 05:31:14 GMT

thanks, I fig;d that out, time to go to school.. :)

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

Rimbik — Fri, 17 Jul 2009 04:59:27 GMT

If you look @ the PageLoad life cycle then you will see LoadViewState() executes after the Page_Init() so you can not have ViewState values in Page_Init().

Soumen

Re: FAQ: Why do dynamic controls disappear on postback and not raise events?

NisGau — Thu, 16 Jul 2009 16:01:46 GMT

If Viewstate is used to store the value of dynamic contrlols then Page_Load is the event to be used. ViewState values are available in Page_Load - but they are not available during the Page_Init event.