I was facing an issue where I want to retrieve existing/active ViewModels from the Prism runtime.

Here’s the code I’ve done to achieve it:

public class ViewModelFinder {   readonly IRegionManager _RegionManager;   readonly IContainer _Container;   public ViewModelFinder(IContainer container, IRegionManager regionManager)   {     _RegionManager = regionManager;     _Container = container;   }    public TViewModel FindOrResolve<TViewModel>()     where TViewModel : class =>     Find<TViewModel>() ?? _Container.Resolve<TViewModel>();    /// <summary>   /// Locates an existing VM in the entire region manager.   /// </summary>   public TViewModel Find<TViewModel>() => (TViewModel)Find(typeof(TViewModel));   public object Find(Type viewModelType)   {     var shellContext = Application.Current.MainWindow.DataContext;     if (shellContext != null && viewModelType.IsAssignableFrom(shellContext.GetType()))       return shellContext;      foreach (var region in _RegionManager.Regions)     {       var viewModel = Find(region, viewModelType);       if (viewModel != null)         return viewModel;     }     return null;   }    /// <summary>   /// Locates an existing VM in the specified region.   /// </summary>                                        public TViewModel Find<TViewModel>(IRegion region) =>    (TViewModel)Find(region, typeof(TViewModel));   public object Find(IRegion region, Type viewModelType)   {     foreach (var view in region.Views.OfType<FrameworkElement>())       if (view.DataContext != null &&       viewModelType.IsAssignableFrom(view.DataContext.GetType()))         return view.DataContext;     return null;   }    } 

It’s intended to be used from any VM, by adding a ViewModelFinder to its constructor to be resolved by the IoC (in my case DryIoc).

When requesting for a VM, it will check for the Shell, then iterate over all views in all regions until it finds the desired VM.

Would love to hear about any better ways to achieve this.