check box validation for atleast one check box should cheked in asp.net

Question

I have asp.net form having 4 check boxes. not check box list. these 4 check boxes having the ValidationGroup property with same name say "chkValied". I have added Custom Validator there. now want to check at least on check box should be check out of these. what to do ?

Answer 1

You can use CustomValidator to validate input at client-side or server-side code.

aspx markup

<asp:CheckBox ID="CheckBox1" runat="server" />
<asp:CheckBox ID="CheckBox2" runat="server" />
<asp:CheckBox ID="CheckBox3" runat="server" />
<asp:CheckBox ID="CheckBox4" runat="server" />

<asp:CustomValidator 
      ID="CustomValidator1" 
      runat="server" 
      ErrorMessage="put here error description"
      ClientValidationFunction="clientfunc" 
      OnServerValidate="CheckValidate">
</asp:CustomValidator>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />

.cs (code-behind)

protected void CheckValidate(object source, ServerValidateEventArgs args)
    {
        args.IsValid=false;
        if (CheckBox1.Checked)
            args.IsValid = true;
        if (CheckBox2.Checked)
            args.IsValid = true;
        if (CheckBox3.Checked)
            args.IsValid = true;
        if (CheckBox4.Checked)
            args.IsValid = true;

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (IsValid)
        {
            //valid
        }
        else
        {
            //Invalid
        }
    }

JavaScript code

 <script type="text/javascript">
        function clientfunc(sender, args) {
            args.IsValid = false;
            if (document.getElementById("CheckBox1").checked)
                args.IsValid = true;
            if (document.getElementById("CheckBox2").checked)
                args.IsValid = true;
            if (document.getElementById("CheckBox3").checked)
                args.IsValid = true;
            if (document.getElementById("CheckBox4").checked)
                args.IsValid = true;
        }
 </script>

Answer 2

Try this article

http://weblogs.asp.net/samirgeorge/archive/2009/05/02/checkboxlist-client-side-validation-using-jquery.aspx

https://web.archive.org/web/20211020153246/https://www.4guysfromrolla.com/webtech/tips/t040302-1.shtml

Answer 3

If you are using custom validator such thing could be achieved with an or-statement:

if (chkBox1.Checked || chkBox2.Checked || chkBox3.Checked)
{
   // At least 1 checkbox was checked.
}

This applies to all languages (although || is not universal all languages has a representation of it). In JavaScript you'd want .Value instead of .Checked.