Multiple Select (MultiSelect) DropDownList with CheckBoxes

DropDownList>

function popup(obj) {
// alert(obj.value);
var company = obj.value
debugger;
$.ajax({
type: "POST",
url: "TML_GST_Invoice_Adjust.aspx/getBu",
data: "{company:" + JSON.stringify(company) + "}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (r) {
var ddlbu1 = $("[id*=ddlbu1]");
ddlbu1.empty();
$.each(r.d, function () {
//alert(this['Value'])

ddlbu1.append($("option>").val(this['Value']).html(this['Text']));
});
}
});

}

but my drop down not bind i debug the code there is no error.