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reference a control that has been dynamically created

Posted on 2011-03-19
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Last Modified: 2012-05-11
I have a web project created with vs2008 and .net 3.5.  I have created a radiobuttonlist control in a table cell dynamically by adding the control to the tablecell.controls collection.  The problem is that I can't retrieve this control from code behind on a button click, the tablecell.controls collection returns 0 as the count.

How can I do this?  I need to read the radiobuttonlist selection to perform an action.
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Question by:dhenderson12
8 Comments
 
LVL 74

Accepted Solution

by:
käµfm³d   👽 earned 125 total points
ID: 35174206
When/where are you adding the controls? Load, PreInit, PreRender, etc.
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LVL 35

Assisted Solution

by:Miguel Oz
Miguel Oz earned 250 total points
ID: 35174285
Where are you keeping your control's state?
Without it, your table cannot remember the dynamic controls when you postback the page (button click)

For state implementation, check:
http://www.codeproject.com/KB/aspnet/state_management_intro.aspx
http://msdn.microsoft.com/en-us/library/75x4ha6s.aspx
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LVL 29

Assisted Solution

by:anarki_jimbel
anarki_jimbel earned 125 total points
ID: 35177071
I believe the easiest way is to have a declaration for a control of this type on a, say, class level, something like:

RadioButtonList rbl = null;

In some method call you create a new RadioButtonList object and add it to a cell. You may create it like:

rbl = new RadioButtonList();...
// do all stuff to fill it etc


Now you may check anywhere in your code that if( rbl!=null) you can do something with it.

Should be pretty simple.

In some more complex cases when you need to create a number of similar controls (and you don't know how many in advance)  you may add them, say, to a Dictionary or to a List etc.

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Author Comment

by:dhenderson12
ID: 35184606
Sorry, all, seems I didn't provide enough information.  This is a content page that is using a master page.  I have a function called loadPage() that is called from a button click.  The control is defined in an xml file, along with the options:
      <control name="OptionList" type="radio">
         <options>
            <option text="Option1" code="OPT1" />
            <option text="Option2" code="OPT2" />
            <option text="Option3" code="OPT3" />
            <option text="Option4" code="OPT4" />
            <option text="Option5" code="OPT5" />
         </options>
      </control>


Here is the code that write the control on the page:
                  switch (controlType.Value)
                  {
                     case "radio":
                        rl = new RadioButtonList();
                        rl.ID = controlName.Value;
                       
                        rl.SelectedIndexChanged += new EventHandler(rlb_SelectedIndexChanged);


                        var options = item.XPathSelectElement("options");

                        foreach (XElement opt in options.Elements())
                           rl.Items.Add(new ListItem(opt.Attribute("text").Value, opt.Attribute("code").Value));


                        tr = TableSurvey.Rows[2];
                        tc = tr.Cells[0];
                        tc.Text = "Please select an option";

                        tc = tr.Cells[2];
                        tc.Controls.Add(rl);
                        break;
                  }

This displays the control perfectly and the control works as expected, but no event fires and I don't know how to reference the control correctly to try to read it's selection.

I really appreciate you all taking a stab at this.
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Author Comment

by:dhenderson12
ID: 35184616
Forgot to add the event code:
      private void rlb_SelectedIndexChanged(object sender, EventArgs e)
      {
         sOption = ((RadioButtonList) sender).SelectedValue;
      }

sOption is a class level string.
0
 
LVL 35

Assisted Solution

by:Miguel Oz
Miguel Oz earned 250 total points
ID: 35185011
How did you write your control on the page?
void page_load
{
  //code to write control
}

If this is the case then your rlb_SelectedIndexChanged will never contain your desired information because the code is rewriting the RadioButtonList (to default values) before the event is executed. Check page lifecycle:
http://msdn.microsoft.com/en-us/library/ms178472.aspx
You have to review how you keep state in your page. Please post the complete code to provide more details if required.
0
 

Author Comment

by:dhenderson12
ID: 35185771

here is the code behind for the page.  it's only for a single page, so there's nothing missing.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml; //namespace to deal with XML documents
using System.Xml.Linq; //namespace to deal with LINQ to XML classes
using System.Xml.XPath;
using System.Xml.Serialization;
using System.IO;
using TMSSI.BipiDTC;
using System.Web.UI.HtmlControls;

namespace TMSSI.BipiDTC.Pradaxa.Branded
{
   public partial class branded : System.Web.UI.Page
   {
      private static string pageName = null;
      private string xmlTranslations = HttpContext.Current.ApplicationInstance.Server.MapPath("~/Translations.xml");
      private string xmlPages = HttpContext.Current.ApplicationInstance.Server.MapPath("~/WebPageDefinitions.xml");
      RadioButtonList rl = null;      
      private string sOption = null;
     
      protected void Page_Load(object sender, EventArgs e)
      {
         if (!IsPostBack)
         {
            pageName = "script";
            loadPage();
         }


      }

      protected void Button2_Click(object sender, EventArgs e)
      {
         fetchNextPage();
      }


      protected void Button1_Click(object sender, EventArgs e)
      {

      }



      private void fetchNextPage()
      {
         switch (pageName)
         {
            case "script":
               System.Diagnostics.Debug.WriteLine("Option: " + sOption);
               break;

         }



      }



      private void fetchLastPage()
      {

      }



      private void loadPage()
      {
         XElement xml = XElement.Load(xmlPages);
         foreach (XElement child in xml.Elements())
            System.Diagnostics.Debug.WriteLine(child);

         TableRow tr = null;
         TableCell tc = null;

         string val = "/webPage[@name='" + pageName + "']";

         var pages = xml.XPathSelectElements(val);
         foreach (XElement item in pages.Elements())
         {
            System.Diagnostics.Debug.WriteLine(item.Name.ToString());

            switch (item.Name.ToString())
            {
               case "formTitle":
                  XAttribute title = item.Attribute("title");

                  tr = TableSurvey.Rows[0];
                  tc = tr.Cells[0];
                  tc.Text = title.Value;

                  break;

               case "narration":
                  XAttribute loc = item.Attribute("location");
                  System.Diagnostics.Debug.WriteLine(loc.Value);
                  loc.Value += "/eng";

                  XElement trx = XElement.Load(xmlTranslations);
                  var xlat = trx.XPathSelectElement(loc.Value);

                  tr = TableNarration.Rows[0];
                  tc = tr.Cells[0];
                  tc.Text = xlat.Value;

                  break;

               case "control":
                  XAttribute controlType = item.Attribute("type");
                  XAttribute controlName = item.Attribute("name");

                  switch (controlType.Value)
                  {
                     case "radio":
                        rl = new RadioButtonList();
                        rl.ID = controlName.Value;
                       
                        rl.SelectedIndexChanged += new EventHandler(rlb_SelectedIndexChanged);


                        var options = item.XPathSelectElement("options");

                        foreach (XElement opt in options.Elements())
                           rl.Items.Add(new ListItem(opt.Attribute("text").Value, opt.Attribute("code").Value));


                        tr = TableSurvey.Rows[2];
                        tc = tr.Cells[0];
                        tc.Text = "Please select an option";

                        tc = tr.Cells[2];
                        tc.Controls.Add(rl);
                        //form1.Controls.Add(rl);
                        break;
                  }




                  break;

            }


         }




      }


      private void processPage()
      {

      }

      private void rlb_SelectedIndexChanged(object sender, EventArgs e)
      {
         sOption = ((RadioButtonList) sender).SelectedValue;

      }










   }
}
0
 

Author Closing Comment

by:dhenderson12
ID: 35185952
figured it out.  needed to put the code that draws the control in the page_load method.  

thanks to all of you for your help.
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