How to reload the ICollectionView binding to wpf combobox? - wpf

Question

I have one textBox and one combobox in wpf usercontrol. ComboxBox is binded to ICollectionView (CurencyList) which populates Currency Pairs like GBP/EUR,CLP/EUR,USD/EUR,EUR/USD etc. Whenever the user writes in textbox e.g. EUR the combobox should get filtered and display the dropdownlist with EUR as the second currency.
For this I have used like:
public string Currency
{
get {
return _criteriaType.currency; }
set
{
if (_criteriaType.currency != value)
{
_criteriaType.currency = value.EmptyOrWhiteSpaceAsNull();
base.OnPropertyChanged("Currency");
CurrencyList.Filter = new Predicate<object>(Contains);
}
}
}
public bool Contains(object de)
{
CurrencyPair o = de as CurrencyPair;
if (Currency != null || Currency == string.Empty)
{
return (o.name.Substring(3, 4).ToLower().Contains(Currency.ToLower()));
}
else
{
IsOpen = false;
OnPropertyChanged("IsOpen");
return false;
}
}
CurrencyList is coming from a webservice:
private ICollectionView GetCurrencyPair()
{
strCurrencyPair.arg0 = (Currency != string.Empty && Currency != null) ? Convert.ToString(Currency).ToUpper() : string.Empty;
string[][] cPair = ServiceLocator.Resolve<IWebServiceRepository>().BusinessWebService.getCurrenyPairs(strCurrencyPair);
foreach (string[] item in cPair)
{
IList.Add(new CurrencyPair() { name = (Convert.ToString(item[0]).ToUpper() + "/" + Convert.ToString(item[1]).ToUpper()) });
}
return CurrencyList =CollectionViewSource.GetDefaultView(IList);
}
Filtering is working fine. But when the user deletes the currency from textbox with backward arrow key from keyboard, the combobox filtered to nothing i.e. dropdownlist is empty.
How to overcome this problem. kindly suggest?

Answer 1

you need to update your collection view through the text change event
private void OnTextChanged(object sender, Eventargs e) {
var vm = yourViewModelOrWhatEver;
((ICollectionView)vm.CurrencyList).Refresh();
}
or set the filter predicate once and fire only the refresh on currency change
public void ctor() {
CurrencyList.Filter = new Predicate<object>(Contains);
}
public string Currency {
get { return _criteriaType.currency; }
set {
if (_criteriaType.currency == value) {
return;
}
_criteriaType.currency = value.EmptyOrWhiteSpaceAsNull();
base.OnPropertyChanged("Currency");
CurrencyList.Refresh(); // refresh/filter the collection view
}
}
hope that helps
EDIT
you say
Filtering is working fine. But when the user deletes the currency from
textbox with backward arrow key from keyboard, the combobox filtered
to nothing i.e. dropdownlist is empty. How to overcome this problem.
kindly suggest?
then you must change your predicate function to this one
public bool Contains(object de)
{
CurrencyPair o = de as CurrencyPair;
if (Currency != null || Currency == string.Empty) {
// Currency == string.Empty should also true
return (Currency == string.Empty) || (o.name.Substring(3, 4).ToLower().Contains(Currency.ToLower()));
} else {
IsOpen = false;
OnPropertyChanged("IsOpen");
return false;
}
}

Answer 2

I would assume the issue lies with this statement: string[][] cPair =
ServiceLocator.Resolve().BusinessWebService.getCurrenyPairs(strCurrencyPair);
what is the return value from that service if you pass string.empty for strCurrencyPair as you will currently be doing once the textbox is empty from backspacing?