How to bind to a singleton property in Silverlight 4?

Hi all first post here :) Let's start with a snippet of the code I'm using:

public MyClass : INotifyPropertyChanged
{
  private static MyClass _instance;
  public static My开发者_开发知识库Class Instance
  {
      get
      {
          if (_instance == null)
              _instance = new MyClass();
          return _instance;
      }
  }

  private bool _myProperty;
  public bool MyProperty
  {
      get
      {
        return _myProperty;
      }
      set
      {
          if (_myProperty!= value)
          {
              _myProperty= value;
              NotifyPropertyChanged("MyProperty");
          }
      }
   }

   private MyClass() { ... }
}

As you can see, it's a singleton class. In my view, I want to bind a control on MyProperty. My initial idea was to import MyClass as a static ressource in my view using something like:

<UserControl x:Class="Metrics.Silverlight.ChartView"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:logic="clr-namespace:Metrics.Logic;assembly=Metrics.Logic">
  <UserControl.Resources>
    <logic:MyClass x:Key="myClass" />
  </UserControl.Resources>
</UserControl>

And bind it like so:

<Button Margin="5" Click="btnName_Click"  Visibility="{Binding Source={StaticResource myClass}, Converter={StaticResource visibilityConverter}, Path=MyAttribute, Mode=OneWay}">

Of course, this approach won't work since MyClass constructor's is private. I also cannot use x:static since it's not available in Silverlight 4.

I've been stuck on this problem far longer than I should have... How can I bind on MyProperty?

Any ideas?

Thanks in advance!

I advice to add additional class MyClassProvider:

public class MyClassProvider
{
    public MyClass MyClass { get { return MyClass.Instance; } }
}

Instance of this class you can place anywhere and bind to its MyClass property.

You could have your UserControl, internally, expose the MyClass instance through it's own property, and bind locally to it's own "MyClass" instance. Since it's a Singleton, this will always be the same instance.

You could implement the singleton slightly differently, like so:

  private static MyClass _instance;
  public MyClass Instance // note the getter is not static
  {
      get
      {
          if (_instance == null)
              _instance = new MyClass();
          return _instance;
      }
  }

so now you could do the following in xaml:

<UserControl x:Class="Metrics.Silverlight.ChartView"
  <UserControl.Resources>
    <logic:MyClass x:Key="myClass" />
  </UserControl.Resources>
</UserControl>

and bind it like this:

<Button Margin="5" Click="btnName_Click"  Visibility="{Binding Source={StaticResource myClass}, Converter={StaticResource visibilityConverter}, Path=Instance.MyAttribute, Mode=OneWay}">

notice that the singleton still is a singleton, but we just bypass Silverlight's missing static by not setting the getter as static.

I have verified the following is working in Silverlight 5:

Keep your class MyClass unchanged, then create an property of MyClass with the name of MyClass in your business UserControl class:

public MyClass MyClass
{
    get { return <Namespace>.MyClass.Instance; }
}

Then in your business UserControl XAML, do binding like this:

<TextBlock Text="Visibility Test" Visiblity="{Binding Path=MyClass.MyProperty, Converter={somexmlns:SomeVisiblityConverterIfNecessary}", ElementName="yourBusinessUserControlName"/>

Once some where in your application, MyClass.Instance.MyProperty (here MyClass is the class name) changes the value of MyProperty, the above binding will be updated.