JQuery check box doesn't keep checked=''checked'

JQuery check box doesn't keep checked=''checked'

I am updating my check box programmatically
$("span[data-id=test] input[type='checkbox']").prop('checked', 'checked');
Visually it works perfect.
But
When I am looking in page source it does't set checked=''checked', if I do
it manually it does.
it dissapere after postback,
I can't use in in ASP.NET in postback events,
I was trying different ways:
.prop('checked', true);
.attr('checked', 'checked');
The same issues..