Migrate from Basic to MVVM and MEF Composable Patterns for a Silverlight Application - Part 3

using System;
using System.ComponentModel.Composition;
using GalaSoft.MvvmLight;
using ProductApp.Common;

namespace AnotherXap.ViewModels
{
    [Export(typeof(IModule)), ExportMetadata(MetadataKeys.Name, ModuleID.AnotherXapViewModel)]
    [PartCreationPolicy(CreationPolicy.NonShared)]
    public class AnotherXapViewModel : ViewModelBase, IModule
    {
        private Lazy<IOtherModel> _lazyAnotherModel;
        private IOtherModel _anotherModel;
        
        public AnotherXapViewModel()
        {
            // Import the lazy model module that can be removed later
            _lazyAnotherModel = ModuleCatalogService.Container.GetExport<IOtherModel>(ModuleID.AnotherXapModel);
            _anotherModel = _lazyAnotherModel.Value;
            
            // Populate the property with data from the Model
            DemoText = _anotherModel.DemoTextData;
        }

        private string _demoText;
        // 
        public string DemoText
        {
            // Property exposed for data binding
            get { return _demoText; }
            set
            {
                if (!ReferenceEquals(_demoText, value))
                {
                    _demoText = value;
                    RaisePropertyChanged("DemoText");
                }
            }
        }

        public override void Cleanup()
        {
            if (_anotherModel != null)
            {
                // Call Cleanup() in the Model
                _anotherModel.Cleanup();

                // Remove imported lazy Model from the Category Service
                // The parameter is the Lazy object instance, cannot be the Value of the Lazy
                ModuleCatalogService.Container.ReleaseExport<IOtherModel>(_lazyAnotherModel);

                _anotherModel = null;
                _lazyAnotherModel = null;
                _demoText = null;
            }

            // Unregister any message for this ViewModel
            base.Cleanup();
        }                          
    }
}