Set binding value as a parameter on a behavior from another control value in Xamarin Forms - xamarin

Question

I am trying to validate a entry value using the entry behaviors. In order to do that I need to pass the value to behavior class from another control in the same xaml.
I have below two controls
<Entry
x:Name="RegisterQty"
Grid.Column="0"
WidthRequest="120"
TextChanged="RegisterQty_TextChanged"
TextColor="Black"
HorizontalOptions="Start"
VerticalOptions="Center"
FontAttributes="Bold"
PlaceholderColor="Black"
Keyboard="Numeric"
FontSize="20">
<Entry.Behaviors>
<local:RegisterQtyBehavior LoadQty = "{Binding BindingContext.qty, Source={x:Reference RegisterQty}} "/>
</Entry.Behaviors>
</Entry>
public class RegisterQtyBehavior : Behavior<Entry>
{
public static readonly BindableProperty LoadQtyProperty = BindableProperty.Create(nameof(LoadQty), typeof(double), typeof(RegisterQtyBehavior), 0);
public double LoadQty
{
get { return (double)GetValue(LoadQtyProperty); }
set { SetValue(LoadQtyProperty, value); }
}
protected override void OnAttachedTo(Entry entry)
{
entry.TextChanged += OnEntryTextChanged;
base.OnAttachedTo(entry);
}
protected override void OnDetachingFrom(Entry entry)
{
entry.TextChanged -= OnEntryTextChanged;
base.OnDetachingFrom(entry);
}
void OnEntryTextChanged(object sender, TextChangedEventArgs args)
{
double result = LoadQty;
bool isValid = double.TryParse(args.NewTextValue, out result);
((Entry)sender).TextColor = isValid ? Color.Red : Color.Default;
}
}
I want to pass label binding Qty to entry control. How could i achieve this? Adding directly LoadQty = "{Binding Qty}"
does not work.

Answer 1

According to your description, you want to parameter in entry behaviors using binding, am I right? if yes, I do one sample you can take a look:
<Entry x:Name="registerqty">
<Entry.Behaviors>
<local:RegisterQtyBehavior LoadQty="{Binding BindingContext.qty, Source={x:Reference registerqty}}}" />
</Entry.Behaviors>
</Entry>
public partial class Page37 : ContentPage, INotifyPropertyChanged
{
private int _qty;
public int qty
{
get { return _qty; }
set
{
_qty = value;
RaisePropertyChanged("qty");
}
}
public Page37 ()
{
InitializeComponent ();
qty = 100;
this.BindingContext = this;
}
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public class RegisterQtyBehavior:Behavior<Entry>
{
public static readonly BindableProperty LoadQtyProperty = BindableProperty.Create("LoadQty", typeof(int), typeof(RegisterQtyBehavior), defaultValue: 0);
public int LoadQty
{
get { return (int)GetValue(LoadQtyProperty); }
set
{
SetValue(LoadQtyProperty,value);
}
}
protected override void OnAttachedTo(Entry entry)
{
entry.TextChanged += OnEntryTextChanged;
base.OnAttachedTo(entry);
}
protected override void OnDetachingFrom(Entry entry)
{
entry.TextChanged -= OnEntryTextChanged;
base.OnDetachingFrom(entry);
}
void OnEntryTextChanged(object sender, TextChangedEventArgs args)
{
//double result;
//bool isValid = double.TryParse(args.NewTextValue, out result);
//((Entry)sender).TextColor = isValid ? Color.Default : Color.Red;
if(!string.IsNullOrEmpty(args.NewTextValue))
{
if (Convert.ToInt32(args.NewTextValue) > LoadQty)
{
((Entry)sender).TextColor = Color.Red;
}
else
{
((Entry)sender).TextColor = Color.Default;
}
}
}
}