Snippet in jQuery

HTML

<div>Select All: <input id="Invitation" type="checkbox" onclick="selectAll(this)" /></div>
<div style="float: left; width: 50%; overflow: hidden;">
  <fieldset>
    <legend></legend>
    0:<input id="InvitationEmail0" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    1:<input id="InvitationEmail1" type="checkbox" value="[email protected]" />   
    <div class="clr"></div>
    2:<input id="InvitationEmail2" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    3:<input id="InvitationEmail3" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    4:<input id="InvitationEmail4" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    5:<input id="InvitationEmail5" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    6:<input id="InvitationEmail6" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    7:<input id="InvitationEmail7" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    8:<input id="InvitationEmail8" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    9:<input id="InvitationEmail9" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    10:<input id="InvitationEmail10" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
    11:<input id="InvitationEmail11" type="checkbox" value="[email protected]" />
    <div class="clr"></div>
  </div>
</fieldset>

CSS

.clr { clear: both; }

JavaScript

function selectAll(obj) {
    $("input[id^=InvitationEmail]").prop("checked", $(obj).prop("checked"));
}