如何在Prism中访问XAML页面的代码隐藏(Xamarin Forms)中的视图模型实例

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
             prism:ViewModelLocator.AutoWireViewModel="True">
    <!-- 页面内容 -->
</ContentPage>

using Prism.Mvvm;

public class MyViewModel : BindableBase
{
    private string _message;
    public string Message
    {
        get { return _message; }
        set { SetProperty(ref _message, value); }
    }

    // 其他属性和命令的定义
}

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
             prism:ViewModelLocator.AutoWireViewModel="True">
    <StackLayout>
        <Label Text="{Binding Message}" />
        <!-- 其他控件 -->
    </StackLayout>
</ContentPage>