How can I validate that all checkboxes in a repeater are checked

Question

I have a form that is pulling in required agreement text from a database and displaying each active agreement clause as a separate checkbox in a repeater. I need to validate that ALL checkboxes in the repeater are checked before the form will submit. Is there a way to do this, or should I go about accomplishing this in a different way than what I have started below?

Currently, I have a CustomValidator, but it only requires that at least one of the checkboxes is checked.

<h1>Agreements</h1>
        <asp:Repeater ID="rptAgreements" runat="server">
            <HeaderTemplate>
                <table>
            </HeaderTemplate>
            <ItemTemplate>
                <tr>
                    <td valign="top" style="padding:10px;">
                        <asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="*" ClientValidationFunction = "ValidateCheckBox"></asp:CustomValidator>
                        <asp:CheckBox ID="Agreements" value='<%# Eval("AgreementID") %>' runat="server" ClientIDMode="Static" />
                    </td>
                    <td style="padding:10px;">
                        <asp:Label ID="lblAgreementText" runat="server" Text='<%# Eval("AgreementText") %>' />
                    </td>
                </tr>
            </ItemTemplate>
            <FooterTemplate>
                </table>
            </FooterTemplate>
        </asp:Repeater>

<script type = "text/javascript">
    function ValidateCheckBox(sender, args) {
        if (document.getElementById("Agreements").checked == true) {
            args.IsValid = true;
        } else {
            args.IsValid = false;
        }
    }
</script> 

Code Behind:

try
    {
        using (SqlConnection con = new SqlConnection(FormConnstring))
        {
            using (SqlCommand cmd = new SqlCommand("sp_SelectAgreements", con))
            {
                using (SqlDataAdapter agreeDS = new SqlDataAdapter(cmd))
                {
                    cmd.CommandType = CommandType.StoredProcedure;
                    DataTable dt = new DataTable();
                    agreeDS.Fill(dt);
                    rptAgreements.DataSource = dt;
                    rptAgreements.DataBind();
                }
            }
        }
    }

Answer 1

You are assigning ClientIDMode="Static" in your code which will generate duplicate Ids in Html and it is not a valid html.

you can assign class for your check boxes and in JS count the agreement check boxes and selected ones then you can compare the numbers. such as bellow:

<input type="checkbox" class="agreement" value="1"> agreement 1
<input type="checkbox" class="agreement" value="2"> agreement 2
<input type="checkbox" class="agreement" value="3"> agreement 3
<input type="checkbox" class="agreement" value="4"> agreement 4
<input type="submit" value="GO" id="btn" />

$('#btn').click(function(){
  var chkAll=$('input.agreement').length;
  var chkSelected = $('input.agreement:checked').length;
  alert(chkAll==chkSelected);
});