public object Convert(IList <object> values, Type targetType, object parameter, CultureInfo culture)
{
if (BindingNotification.ExtractValue(values[0]) == AvaloniaProperty.UnsetValue)
{
return(AvaloniaProperty.UnsetValue);
}
var condition = (bool)BindingNotification.ExtractValue(values[0]);
var trueResult = (object)values[1];
var falseResult = (object)values[2];
return(condition ? trueResult : falseResult);
}
private static object Negate(object?value)
{
var notification = value as BindingNotification;
var v = BindingNotification.ExtractValue(value);
BindingNotification GenerateError(Exception e)
{
notification ??= new BindingNotification(AvaloniaProperty.UnsetValue);
notification.AddError(e, BindingErrorType.Error);
notification.ClearValue();
return(notification);
}
if (v != AvaloniaProperty.UnsetValue)
{
var s = v as string;
if (s != null)
{
bool result;
if (bool.TryParse(s, out result))
{
return(!result);
}
else
{
return(GenerateError(new InvalidCastException($"Unable to convert '{s}' to bool.")));
}
}
else
{
try
{
var boolean = Convert.ToBoolean(v, CultureInfo.InvariantCulture);
if (notification is object)
{
notification.SetValue(!boolean);
return(notification);
}
else
{
return(!boolean);
}
}
catch (InvalidCastException)
{
// The error message here is "Unable to cast object of type 'System.Object'
// to type 'System.IConvertible'" which is kinda useless so provide our own.
return(GenerateError(new InvalidCastException($"Unable to convert '{v}' to bool.")));
}
catch (Exception e)
{
return(GenerateError(e));
}
}
}
return(notification ?? AvaloniaProperty.UnsetValue);
}
