hello I see this example ( demos/jqxcombobox/settings.htm )
http://www.jqwidgets.com/jquery-widgets-demo/demos/jqxcombobox/index.htm?(arctic)#demos/jqxcombobox/settings.htm
and is working

but it does not work on my project
I think case sensitive works
$('#test').jqxComboBox({
source: dataSource,
promptText: "Select Item",
displayMember: "Name",
valueMember: "ID",
height: "28px",
width: "100%",
searchMode: 'contains',
autoComplete: true,
selectedIndex: 0,
theme: "web",
});
$('#test').jqxComboBox('insertAt', { label: "Select Item", value: 0 }, 0);
`

I use jQWidgets v3.7.0 (2015-Feb)
sample code
http://jsfiddle.net/6H8ae/48/
thank you