FindControl cannot find checkbox in c#

Question

I have checkboxes created in a repeater:

<asp:Repeater ID="companyRepeater" runat="server">
    <ItemTemplate>
        <tr class ="DGItemStyle" id="myresultsRow1" runat="server" style='<%# SetBoxVisibilityReverse(Eval("compnName1").ToString()) %>'> 
            <td  style="padding:0.5em;"><%#Eval("compnAddress1") %></td> 
            .....
            <td><asp:CheckBox id="foo" runat="server" AutoPostBack="True" name="foo" /></td>
        </tr>

I want to find out which checkbox is currently selected by user, so in the codebehind I do:

CheckBox chkbox_All = FindControl("foo") as CheckBox;
if (chkbox_All != null)
{
   if (!chkbox_All.Checked)
   {
       Response.Write("No checked");
   }
   else
   {
       var IDs = chkbox_All.ClientID;
       Response.Write("ID here...");
   }
}

But what I found is that the chkbox_All is always null no matter how many checkboxes are selected. Why is it so and how could I find which checkbox is checked in this case ?

ekad · Accepted Answer · 2014-12-22 06:46:55Z

2

You need to enumerate through companyRepeater.Items using a foreach block as below

foreach (RepeaterItem ri in companyRepeater.Items)
{
    CheckBox chkbox_All = ri.FindControl("foo") as CheckBox;
    if (chkbox_All != null)
    {
       if (!chkbox_All.Checked)
       {
           Response.Write("No checked");
       }
       else
       {
           var IDs = chkbox_All.ClientID;
           Response.Write("ID here...");
       }
    }
}

EDIT

If you want to display the ID of the checked checkboxes, add a Literal somewhere outside the repeater

<asp:Literal ID="ltChecked" runat="server" />

and add the id to ltChecked.Text if the checkbox is checked

foreach (RepeaterItem ri in companyRepeater.Items)
{
    CheckBox chkbox_All = ri.FindControl("foo") as CheckBox;
    if (chkbox_All != null)
    {
       if (chkbox_All.Checked)
       {
           ltChecked.Text += chkbox_All.ClientID;
           ltChecked.Text += ", ";
       }
    }
}

EDIT 2

To prevent the page reload when checking the checkbox, remove AutoPostBack="True" from the foo checkbox

<asp:Repeater ID="companyRepeater" runat="server">
    <ItemTemplate>
        <tr class = "DGItemStyle"  id="myresultsRow1" runat="server" style='<%# SetBoxVisibilityReverse(Eval("compnName1").ToString()) %>'> 
            <td  style="padding:0.5em;"><%#Eval("compnAddress1") %></td> 
            .....
            <td><asp:CheckBox id="foo" runat="server" name="foo" /></td>
        </tr>

EDIT 3

To get the compnName1 value from the same row as the checked checkbox, add a hidden field (hdCompName) that holds the compnName1 value in the repeater

<asp:Repeater ID="companyRepeater" runat="server">
    <ItemTemplate>
        <tr class = "DGItemStyle"  id="myresultsRow1" runat="server" style='<%# SetBoxVisibilityReverse(Eval("compnName1").ToString()) %>'> 
            <td  style="padding:0.5em;"><%#Eval("compnAddress1") %></td> 
            .....
            <td><asp:CheckBox id="foo" runat="server" name="foo" />
                <asp:HiddenField id="hdCompName" runat="server" Value='<%# Eval("compnName1") %>' />
            </td>
        </tr>

then get the value of hdCompName in the code behind as below

foreach (RepeaterItem ri in companyRepeater.Items)
{
    CheckBox chkbox_All = ri.FindControl("foo") as CheckBox;
    if (chkbox_All != null)
    {
        if (chkbox_All.Checked)
        {
            HiddenField hdCompName = ri.FindControl("hdCompName") as HiddenField;
            ltChecked.Text += hdCompName.Value;
            ltChecked.Text += ", ";
        }
    }
}

edited Dec 22, 2014 at 6:46

answered Dec 22, 2014 at 3:34

ekad

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11 Comments

user1314404 Over a year ago

Yes, thats right! Then do you know how could I identify which checkbox is checked?

ekad Over a year ago

You can use a Label or Literal outside of the repeater and set the Text property to the ID of the checked checkboxes.

ekad Over a year ago

It's because of AutoPostBack="True", you need to remove it as in the EDIT 2 section.

ekad Over a year ago

Yes it's possible, use a hidden field as described in EDIT 3 section.

ekad Over a year ago

Did you change your repeater code exactly as the code in EDIT 3 section?

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