How to implement input checkbox's checked action?

In a WebForm I have an input checkbox to which I wanna apply server side action. For example, when the checkbox is checked, I want to change some label's text. I have tried to use on client side:

<input id="auto" name="auto" type="checkbox" data-toggle="toggle" data-on="AUTOMAT" data-off="MANUAL" <%= string.IsNullOrEmpty(Request["auto"]) ? string.Empty : "checked" %> />
<asp:Label ID="Label3" runat="server" Text="Label"></asp:Label>   
<asp:HiddenField ID="customSwitch1Change" runat="server" Value="0" />
        <script>
            $('#auto').click(function () {
                $('#<%=customSwitch1Change.ClientID%>').val("1");
                $('#form1').submit();
            });
        </script>

I have used this and this for the input checkbox.

On the server-side I have tried:

protected void CustomSwitch1Change(string auto)
{

    if (string.IsNullOrEmpty(auto))
    {
        Label3.Text = $"customSwitch1 was not checked.";
    }
    else
    {
        Label3.Text = $"customSwitch1 was checked and the check value is {auto}.";
    }
}

But what I've tried is not working. What I'm doing wrong? Or is there another way to do this?