Not firing the SelectedIndexChanged when using jquery combobox

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C#

ASP.NET

Javascript

jQuery

I have a form with a ComboBox that provides a dropdownlist with loaded values from db.

Now the problem is when I am selecting a value from the combobox, the event dllTest_SelectedIndexChanged is not firing from code behind.

<asp:DropDownList ID="dllTest" runat="server" AutoPostBack="true" OnSelectedIndexChanged="dllTest_SelectedIndexChanged">

and I am calling the combobox from a jquery

$("#<%=dllTest.ClientID%>").combobox();

I tried

$('#dllTest').combobox();

and add the property of the dropdown ClientIDMode="Static" and still not working