function bindDropDownList(e, targetDropDownList) 
{
    var key = this.value;
    var allOptions = targetDropDownList.allOptions;
    var option;
    var newOption;
    targetDropDownList.options.length = 0;

    newOption = new Option('Todas las ciudades', '');
    targetDropDownList.options.add(newOption);
    
    for (var i=0; i < allOptions.length; i++) 
    {
        option = allOptions[i];
        if (option.key == key) 
        {
            newOption = new Option(option.text, option.value);
            targetDropDownList.options.add(newOption);
        }
    }
}

function CascadingDropDownListDefaults(ctrlName, key, desc) {
    var ctrl = document.getElementById(ctrlName);
    if (ctrl) {
        newOption = new Option(desc, key);
        ctrl.options.add(newOption);
    }
}