Validate Asp.Net checkbox list using Custom validator .

In this article , I have explained how to validate Asp.net checkboxlist using custom validator means I have to select atleast one checkbox from checkboxlist.

Put the checkboxlist control on design page and add some items in it and one cutome validator and one button.

<asp:CheckBoxList ID="CheckBoxList1" runat="server">

    <asp:ListItem Text="c#"></asp:ListItem>

    <asp:ListItem Text="ASP"></asp:ListItem>

    <asp:ListItem Text="Asp.Net"></asp:ListItem>

    <asp:ListItem Text="Sql"></asp:ListItem>

    <asp:ListItem Text="Ajax"></asp:ListItem>

    </asp:CheckBoxList>

    <asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="Please select atleast one item from list." ForeColor="Red"

    ClientValidationFunction="ValidateCheckBoxList"></asp:CustomValidator>

    <asp:Button ID="Button1" runat="server" Text="Submit" />

JavaScript Function:-

Here I have written javascript function for selecting atleast one checkbox from checkboxlist and called this method on custom validator.

This function is executed when cutom validator is trigered on button click.

If checkbox is checked then isvalid value set to true else false.

<script type="text/javascript">

    function ValidateCheckBoxList(sender, args) {

    var checkBoxList=document.getElementById("<%=CheckBoxList1.ClientID %>");

    var checkBox=document.getElementsByTagName("input");

    var isvalid=false;

    for(var i=0;i<checkBox.length;i++)

    {

        if (checkBox[i].checked) {

            isvalid = true;

            break;

        }

    }

    args.IsValid = isvalid;

    }

</script>