CompositeCommand with Feedback of ICommands

Hi,

in my masterthesis i decided to use some .net techniques. The appication is written in c#/wpf with the prism library regarding to architekture. Now i got a problem on the feedback of single commands, seperated executed in a composite command.

I want to import some huge files for my model so i need some kind of feedback. I have written an ICommand for each file and made it asynchronously running with the async/await operators. An example of these files look like this:

class ImportMaterialFile : ICommand
{
    #region Members

    ImportFileViewModel materialFile;
    public ObservableCollection<ImportErrorViewModel> errors = new ObservableCollection<ImportErrorViewModel>();

    Int16 numberOfLines = 0;
    Int16 processedLines = 0;

    #endregion

    #region ICommand Members

    public bool CanExecute(object param)
    {
        var container = ServiceLocator.Current.GetInstance<IUnityContainer>();
        InterfaceViewModel interfaceViewModel = (InterfaceViewModel)container.Resolve<IInterfaceViewModel>();

        bool CanExecute = false;

        foreach (ImportFileViewModel importFile in interfaceViewModel.SapFeliosInterfaceFiles)
        {
            if (importFile.FileName.Split('.').First().Contains("MAT"))
            {
                materialFile = importFile;
                try
                {
                    StreamReader reader = new StreamReader(materialFile.FilePath);
                    string line;
                    while ((line = reader.ReadLine()) != null)
                    {
                        numberOfLines++;
                    }
                    CanExecute = true;
                }
                catch (Exception ex)
                {
                    errors.Add(new ImportErrorViewModel(ex.ToString(), materialFile.FileName, 0));
                }
            }
        }

        return CanExecute;
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public async void Execute(object param)
    {
        await ImportAsync();
    }

    #endregion

    #region Private Methods

    private Task ImportAsync()
    {
        return Task.Run(() => Import());
    }

    private void Import()
    {
        var container = ServiceLocator.Current.GetInstance<IUnityContainer>();
        InterfaceViewModel interfaceViewModel = (InterfaceViewModel)container.Resolve<IInterfaceViewModel>();

        try
        {
            StreamReader streamReader = new StreamReader(materialFile.FilePath);
            String line;
            Int16 counter = 1;

            Material material;

            while ((line = streamReader.ReadLine()) != null)
            {
                try
                {
                    material = new Material();

                    //set properties from line

                    interfaceViewModel.ModelSapFeliosContainer.MaterialSet.Add(material);

                    counter++;
                    processedLines++;
                }
                catch (Exception ex)
                {
                    errors.Add(new ImportErrorViewModel(ex.ToString(), materialFile.FileName, counter));
                }
            }

            interfaceViewModel.ModelSapFeliosContainer.SaveChanges();
        }
        catch (Exception ex)
        {
            MessageBox.Show("error while reading MAT-File\n\n" + ex.ToString());
        }
    }

    #endregion
}

I have to execute three of these files in a compositecommand which looks like this.

class ImportSapFeliosInterfaceFiles : CompositeCommand
    {
        #region Members

        ImportProcessingPointFile importProcessingPointFile = new ImportProcessingPointFile();
        ImportMaterialFile importMaterialFile = new ImportMaterialFile();
        ImportProductionOrderFile importProductionOrderFile = new ImportProductionOrderFile();
        ImportProductionOrderStepFile importProductionOrderStepFile = new ImportProductionOrderStepFile();

        ObservableCollection<ImportErrorViewModel> errors = new ObservableCollection<ImportErrorViewModel>();
        
        #endregion

        #region Construction

        public ImportSapFeliosInterfaceFiles()
        {
            this.RegisterCommand(importMaterialFile);
            this.RegisterCommand(importProductionOrderFile);
            this.RegisterCommand(importProductionOrderStepFile);
        }

        #endregion

        #region Properties

        public ObservableCollection<ImportErrorViewModel> GetErrors()
        {
            foreach (ImportErrorViewModel ie in importMaterialFile.errors)
            {
                errors.Add(ie);
            }

            foreach (ImportErrorViewModel ie in importProductionOrderFile.errors)
            {
                errors.Add(ie);
            }

            foreach (ImportErrorViewModel ie in importProductionOrderStepFile.errors)
            {
                errors.Add(ie);
            }

            return this.errors;
        }

        #endregion
    }

Now, my actual Problem is, that i want to have one View, giving me a feedback on whats going on. I cant figure out, how to to this. Is this the point where i have to use prisms eventaggregator? Or can i just signature my ICommands as an observableobject?

Some tips, ideas etc would be nice ;)

Tags: C#, WPF, PRISM