Use jQuery to remove options from a SELECT object and add each item from a list to a SELECT object.
//get select object
var selectObject = $("#ddlCountryList");
//remove previous values - optional
$(selectObject).find("option").remove();
//append new values
$.each(array_of_countries, function()
{
selectObject.append($("<option />").val(this.CountryId).text(this.CountryName));
});