MVVM : Share data between ViewModels

Question

How do I share data between multiple ViewModels ?

For example there is a class named Project in application .

    public class Project : ModelBase
{
    private string _projectName;

    public string ProjectName
    {
        get { return _projectName; }
        set
        {
            _projectName = value;
            RaisePropertyChanged(() => ProjectName);
        }
    }
}

In multiple ViewModels application should access ActiveProject.
What's the best way to share Project between ViewModels ?

• Mediator Pattern ? (Messaging)
• Static object
• Singleton pattern (If yes how?)

I've used Messaging before but it needs much codding . For all ViewModels I've to create ActiveProject property and also have to register a messenger to update that.

I use MVVM Light framework.
Any code example would be appreciated.

Answer 1

I would create a ViewModel that acts as a parent to all the Project ViewModels. (Let's call it Solution)

The Solution ViewModel would have the property ActiveProject and an observable collection of Projects.