Check if at least one checkboxlist is selected

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I have checkboxlist and I would like to check if at least one checkbox is checked. If none is checked then I want to show alert message that says please select at least one item. I want to do this in code behind if possible. I have started but don't know if it is right or wrong but not able to finish it.

 public void alert()
    {
        foreach (ListItem listItem in cblCustomerList.Items)
        {
            if (!listItem.Selected)
            {
            }
        }
    }

here is the checkboxlist in aspx:

 <asp:CheckBoxList ID="cblCustomerList" runat="server" DataSourceID="SqlDataSource1" CssClass="CheckBoxList"
            DataTextField="GroupName" DataValueField="GroupName" 
                onclick="readCheckBoxList()" >               
            </asp:CheckBoxList>

here is the button:

 <asp:Button ID="Button1" runat="server" CausesValidation="True" 
                            CommandName="Insert" Text="Insert" OnClientClick="return Validate_Checkbox()" />

Thanks for your help.

Assimilation answered 6/3, 2013 at 15:35 Comment(6)

Should be in JS, rather than in code behind – Cater 6/3, 2013 at 15:37

It is better to do this kind of check on the client side using javascript. There is nothing here that depends on data from server – Halfpenny 6/3, 2013 at 15:38

@both It is really trivially easy to bypass client side validation. It is perfectly reasonable to want code behind validation. – Archaize 6/3, 2013 at 15:39

The alert part is what am worried about not the checking. Check is already in the answer. Probably put a label on the page and set the text property to your error message. <asp:Label ForeColor="Red" /> – Halfpenny 6/3, 2013 at 15:42

@Halfpenny +1 for reading comprehension. I didn't even notice that. Asker: are you trying for client side or server side validation? – Archaize 6/3, 2013 at 15:44

either client side or server side will work for me and i already tried jquery but i had some issues with it. – Assimilation 6/3, 2013 at 15:50

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Edit:

Here is one sample code. its working to me

Must add this script file :<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>

 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script type="text/javascript">
        function Validate_Checkbox() {
            var chks = $("#<%= cblCustomerList.ClientID %> input:checkbox");          

            var hasChecked = false;
            for (var i = 0; i < chks.length; i++) {
                if (chks[i].checked) {
                    hasChecked = true;
                    break;
                }
            }
            if (hasChecked == false) {
                alert("Please select at least one checkbox..!");

                return false;
            }

            return true;
        }     
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:CheckBoxList ID="cblCustomerList" runat="server" CssClass="CheckBoxList">
            <asp:ListItem Value="0">xx</asp:ListItem>
            <asp:ListItem Value="1">yy</asp:ListItem>
        </asp:CheckBoxList>
        <asp:Button ID="xx" runat="server" OnClientClick="javascript:Validate_Checkbox();return true;" />
    </div>
    </form>
</body>
</html>

and you change

<asp:CheckBoxList ID="cblCustomerList" runat="server" DataSourceID="SqlDataSource1" CssClass="CheckBoxList" DataTextField="GroupName" DataValueField="GroupName">             
            </asp:CheckBoxList>

control instead of my sample code . and call the javascript function in the button control.look my sample code.

Chears!!!

Edit

please add this script file

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>

Instead of <script src="scripts/jquery-1.8.3.min.js" type="text/javascript"></script>

Doubletalk answered 6/3, 2013 at 15:39 Comment(8)

my control id is called cblCustomerList where are you calling that in the javascript? here is my checkboxlist in aspx: <asp:CheckBoxList ID="cblCustomerList" runat="server" DataSourceID="SqlDataSource1" CssClass="CheckBoxList" DataTextField="GroupName" DataValueField="GroupName" onclick="readCheckBoxList()" > </asp:CheckBoxList> – Assimilation 6/3, 2013 at 15:58

I have new edited code above .please check the new code. its working – Doubletalk 6/3, 2013 at 16:4

thanks but it is showing the alert eventhough i have selected one item. i am not sure what is going on please help thanks – Assimilation 6/3, 2013 at 18:36

Hey my new Edit code is working fine in my local. You just change check box control . – Doubletalk 6/3, 2013 at 19:14

i am getting different error that reads like this:"Error: Object doesn't support this property or method". the OnClientClick is not tied to the checkboxlist but it is tied to a button. pls. see my updated code above. thanks – Assimilation 6/3, 2013 at 19:31

Are you assign this script file?? <script src="scripts/jquery-1.8.3.min.js" type="text/javascript"></script> – Doubletalk 6/3, 2013 at 19:33

I think the 1.8.3 min version script not have you. So just add this script <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script> instead of my script and i also now changed new code.You can try my new code.its working to me.any doubt .please let me. i am waiting – Doubletalk 6/3, 2013 at 19:39

it worked like a charm even though i used <script src="../Scripts/jquery-1.8.1.min.js" type="text/javascript"></script>. Your revised code worked very nice. thank you so much for your help – Assimilation 6/3, 2013 at 20:36

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if(cblCustomerList.Items.Cast<ListItem>().Any(item => item.Selected))
{
   // at least one selected
}

Klipspringer answered 6/3, 2013 at 15:37 Comment(0)

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