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using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using Xamarin.Forms.Platform;
namespace Xamarin.Forms
{
[RenderWith(typeof(_PickerRenderer))]
public class Picker : View
{
public static readonly BindableProperty TitleProperty = BindableProperty.Create("Title", typeof(string), typeof(Picker), default(string));
public static readonly BindableProperty SelectedIndexProperty = BindableProperty.Create("SelectedIndex", typeof(int), typeof(Picker), -1, BindingMode.TwoWay,
propertyChanged: (bindable, oldvalue, newvalue) =>
{
EventHandler eh = ((Picker)bindable).SelectedIndexChanged;
if (eh != null)
eh(bindable, EventArgs.Empty);
}, coerceValue: CoerceSelectedIndex);
public Picker()
{
Items = new ObservableList<string>();
((ObservableList<string>)Items).CollectionChanged += OnItemsCollectionChanged;
}
public IList<string> Items { get; }
public int SelectedIndex
{
get { return (int)GetValue(SelectedIndexProperty); }
set { SetValue(SelectedIndexProperty, value); }
}
public string Title
{
get { return (string)GetValue(TitleProperty); }
set { SetValue(TitleProperty, value); }
}
public event EventHandler SelectedIndexChanged;
static object CoerceSelectedIndex(BindableObject bindable, object value)
{
var picker = (Picker)bindable;
return picker.Items == null ? -1 : ((int)value).Clamp(-1, picker.Items.Count - 1);
}
void OnItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
SelectedIndex = SelectedIndex.Clamp(-1, Items.Count - 1);
}
}
}
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