BindableProperty (List<>) in Xamarin Forms

Question

my problem is the following: I have my ContentPage which has a ResourceDictionary with some DataTemplates. One of the templates takes the Horse Object (which holds the List<Weight>'s). I display several stats of that object but when I want to pass variables from the Horse Object to another view such as the following:

<graph:LineGraph x:Name="displayWeight" WeightOfHorse="{Binding Weight}"/>

Code Behind WeightOfHorse:

public static readonly BindableProperty WeightOfHorseProperty = BindableProperty.Create(
    nameof(WeightOfHorse),
    typeof(IList<Weight>),
    typeof(LineGraph),
    defaultBindingMode: BindingMode.TwoWay);

public IList<Weight> WeightOfHorse
{
    get => (IList<Weight>)GetValue(WeightOfHorseProperty);
    set => SetValue(WeightOfHorseProperty, value);
}

I just don't manage to pass the values, I know that they are available because I can display them in a simple Collectionview.

What am I doing wrong?

score 2 · Accepted Answer · answered Sep 27 '20 at 08:08

I figured it out, this works. It seems that you need to assign the property by the changing event.

public static readonly BindableProperty WeightOfHorseProperty = BindableProperty.Create(
nameof(WeightOfHorse),
typeof(IEnumerable<Weight>),
typeof(LineGraph),
defaultBindingMode: BindingMode.TwoWay,
propertyChanged: OnEventNameChanged);

public IEnumerable<Weight> WeightOfHorse
{
get => (IEnumerable<Weight>)GetValue(WeightOfHorseProperty);
set => SetValue(WeightOfHorseProperty, value);
}

static void OnEventNameChanged(BindableObject bindable, object oldValue, object newValue)
{
var control = (LineGraph)bindable;
control.WeightOfHorse = (List<Weight>)newValue;
...
}

Hi, glad have found the solution! Rmember to mark it when you have time, it will be helpful for other people who have the same problem. — Junior Jiang, Sep 28 '20 at 02:01

score 1 · Answer 2 · answered Sep 26 '20 at 17:41

1

Please try to change IList to ObservableCollection.

answered Sep 26 '20 at 17:41

Qwerty

429
2
8

Thanks for that suggestion, what does it matter? Maybe I was unclear, the property was never set. So it seems that it never passes the values. – Daniel Klauser Sep 26 '20 at 21:54

BindableProperty (List<>) in Xamarin Forms

2 Answers2