Xamarin DropDown列表人口

Question

我正在尝试获取一个（国家/地区）列表来填充“Picker”＃39;领域。现在当我运行应用程序并点击列表选择器字段时，我所看到的就是：

代码（.cs）：

 List<string> countries = new List<string>
            {
                ....
                "Western Sahara",
                "Yemen",
                "Yugoslavia",
                "Zambia",
                "Zimbabwe"
            };
            List<string> Countries => countries;

            string SelectedCountry;

            int countriesSelectedIndex;
            public int CountriesSelectedIndex
            {
                get
                {
                    return countriesSelectedIndex;
                }
                set
                {
                    if (countriesSelectedIndex != value)
                    {
                        countriesSelectedIndex = value;

                        // trigger some action to take such as updating other labels or fields
                        OnPropertyChanged(nameof(CountriesSelectedIndex));
                        Country = Countries[countriesSelectedIndex];
                    }
                }
            }  


public string Country
        {
            get
            {
                return _country;
            }
            set
            {
                _country = value;
                OnPropertyChanged(nameof(Country));
            }
        }

代码（.xaml）：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:ViewModels="clr-namespace:LoginSystem.ViewModels"
             BackgroundColor="Azure" 
             x:Class="LoginSystem.Views.UserProfileINC">
    <ContentPage.Content>

        <StackLayout Padding="10" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto"/>
                    <ColumnDefinition Width="*"/>
                    <!--Gender Country Address Province Postal-->
                </Grid.ColumnDefinitions>
                <Label Text="Gender" Grid.Row="0" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
                <Entry Text="{Binding Gender}" Grid.Row="0" Grid.Column="1" />

                <Label Text="Country" Grid.Row="1" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
                <Picker x:Name="picker" Grid.Row="1" Grid.Column="1" SelectedIndex="{Binding CountriesSelectedIndex}" ItemsSource="{Binding Countries}"/>
                <!--<Entry Text="{Binding Country}" Grid.Row="1" Grid.Column="1" />-->


                <Label Text="Address" Grid.Row="2" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
                <Entry Text="{Binding Address}" Grid.Row="2" Grid.Column="1" />
                <Label Text="Province" Grid.Row="3" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
                <Entry Text="{Binding Province}" Grid.Row="3" Grid.Column="1" />
                <Label Text="Postal" Grid.Row="4" Grid.Column="0" HorizontalOptions="Start" VerticalOptions="Center"></Label>
                <Entry Text="{Binding Postal}" Grid.Row="4" Grid.Column="1" />
            </Grid>

            <Button Text="Done!" HorizontalOptions="FillAndExpand" BackgroundColor="Blue" TextColor="White" Command="{Binding Button_Clicked}"/>

        </StackLayout>
    </ContentPage.Content>
</ContentPage>  

这是绑定选择器的行：

<Picker x:Name="picker" Grid.Row="1" Grid.Column="1" SelectedIndex="{Binding CountriesSelectedIndex}" ItemsSource="{Binding Countries}"/>