function unique(arr : ArrayList) : ArrayList {
    var comparer = function compareObject(a, b) {
        if (a.OrderNumber == b.OrderNumber) {
 
                return 0;
 
        } else {
            if (a.OrderNumber < b.OrderNumber) {
                return 1;
            } else {
                return -1;
            }
        }
    }
 
    arr.sort(comparer);
    for (var i = 0; i < arr.length - 1; ++i) {	
        if (comparer(arr[i], arr[i+1]) == 0) {
            arr.removeAt(i);
        }
    }
    return arr;
}