Sharing data between different ViewModels

Question

I\'m trying to develop an easy MVVM project that it has two windows:

1. The first window is a text editor, where I bind some properties such as FontSize

Answer 1

Another option is to store such "shared" variables in a SessionContext-class of some kind:

public interface ISessionContext: INotifyPropertyChanged 
{
    int EditorFontSize { get;set; }
}

Then, inject this into your viewmodels (you are using Dependency Injection, right?) and register to the PropertyChanged event:

public class MainWindowViewModel 
{
    public MainWindowViewModel(ISessionContext sessionContext)
    {
        sessionContext.PropertyChanged += OnSessionContextPropertyChanged;        
    }

    private void OnSessionContextPropertyChanged(object sender, PropertyChangedEventArgs e) 
    {
        if (e.PropertyName == "EditorFontSize")
        {
            this.EditorFontSize = sessionContext.EditorFontSize;
        }
    }       
}