In ASP.NET a number of controls are rendered with the '$' inside the element Id.

Ex. <input type="text" id="txt$sample" class="datebox" />

I can use the following 3 valid selectors to display the datepicker for that box:

$('#txt\\$sample').datepicker(); $("input:text[id$='sample']").datepicker(); $('.datebox').datepicker();

All 3 of these will display the datepicker when the textbox receives focus, but when a date is selected in the datepicker, an exception is thrown.

Once the "$" is removed from the element id, the error goes away.