Xamarin.Forms Bindable Picker

If anyone wonders how to make a Bindable Picker, here's the code:

`

public class BindablePicker : Picker
{
    #region Fields

    //Bindable property for the items source
    public static readonly BindableProperty ItemsSourceProperty =
        BindableProperty.Create<BindablePicker, IEnumerable>(p => p.ItemsSource, null, propertyChanged: OnItemsSourcePropertyChanged);

    //Bindable property for the selected item
    public static readonly BindableProperty SelectedItemProperty =
        BindableProperty.Create<BindablePicker, object>(p => p.SelectedItem, null, BindingMode.TwoWay, propertyChanged: OnSelectedItemPropertyChanged);

    #endregion

    #region Properties

    /// <summary>
    /// Gets or sets the items source.
    /// </summary>
    /// <value>
    /// The items source.
    /// </value>
    public IEnumerable ItemsSource
    {
        get { return (IEnumerable)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    /// <summary>
    /// Gets or sets the selected item.
    /// </summary>
    /// <value>
    /// The selected item.
    /// </value>
    public object SelectedItem
    {
        get { return GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty, value); }
    }

    #endregion

    #region Methods

    /// <summary>
    /// Called when [items source property changed].
    /// </summary>
    /// <param name="bindable">The bindable.</param>
    /// <param name="value">The value.</param>
    /// <param name="newValue">The new value.</param>
    private static void OnItemsSourcePropertyChanged(BindableObject bindable, IEnumerable value, IEnumerable newValue)
    {
        var picker = (BindablePicker)bindable;
        var notifyCollection = newValue as INotifyCollectionChanged;
        if (notifyCollection != null)
        {
            notifyCollection.CollectionChanged += (sender, args) =>
            {
                if (args.NewItems != null)
                {
                    foreach (var newItem in args.NewItems)
                    {
                        picker.Items.Add((newItem ?? "").ToString());
                    }
                }
                if (args.OldItems != null)
                {
                    foreach (var oldItem in args.OldItems)
                    {
                        picker.Items.Remove((oldItem ?? "").ToString());
                    }
                }
            };
        }

        if (newValue == null) 
            return;

        picker.Items.Clear();

        foreach (var item in newValue)
            picker.Items.Add((item ?? "").ToString());
    }

    /// <summary>
    /// Called when [selected item property changed].
    /// </summary>
    /// <param name="bindable">The bindable.</param>
    /// <param name="value">The value.</param>
    /// <param name="newValue">The new value.</param>
    private static void OnSelectedItemPropertyChanged(BindableObject bindable, object value, object newValue)
    {
        var picker = (BindablePicker)bindable;
        if (picker.ItemsSource != null)
            picker.SelectedIndex = picker.ItemsSource.IndexOf(picker.SelectedItem);
    }

    #endregion
}

`

Usage is pretty straight forward..:

<local:BindablePicker ItemsSource="{Binding Cats}" SelectedItem="{Binding SelectedCat}"/>

It would've been nice that the Xamarin.Forms.Picker already had this functionality, maybe we'll see it in a next update...

Any questions, comments, or contributions are welcome