How can my design implement MVVM? - wpf

Question

I have an issue trying to understand how to implement the MVVM pattern in my application. It's a small application and I will explain what it does.
My application creates a backup of files. The UI lets the user choose which folder they want to back up and where it should be backed up too. After making their selection they click the "start" button.
This then passes the folder source and folder destination to a class library (called backup.cs) which creates the back ups of all the files inside each folder. During this, a log (Log.cs) is created logging each stage and the state of each file it attempted to back up (complete, failed, other, etc). Now, the log is in memory only.
When the back up is complete I want a window to open (a view) which will display all the logs. It's at this point I can't understand how to use the MVVM pattern.
As it stands today, I pass my log (which holds the data in a hierarchical way) to my MainWindow's constructor and bind to the datacontext, using a treeview in my xaml I get the desired results. However, I now want to use MVVM.
My question is very similar to my previous question, as you can see the answer is to pass the log as a paramter to the ViewModel constructor. The issue is, I don't know how to do that and also display a window!
The only way (in my head) I can achieve this is by passing the Log as a parameter to a constructor of my View but this defeats the point of the MVVM. I could pass the parameter to my ViewModel's constructor (which would fit the MVVM pattern) but would that then mean I have to also create an instance of my View from my ViewModel constructor as well? Otherwise all I would do is create my ViewModel but have no way to display the results since the View isn't displayed.
I hope I have explained where I'm struggling clearly, can any one suggest a way forward please?

Answer 1

Most likely you 'll want the viewmodel to accept (and expose through a property) a collection such as a List<Log> -- typically this would be an ObservableCollection<Log>, but if the operation has already completed there is no real point in going that way. This is what you are describing as a possible solution.
To wire the viewmodel to the view, in essence you need to do this:
var viewModel = new LogsViewModel(...);
var view = new LogsView(); // no constructor parameters
view.DataContext = viewModel;
And finally you add view at some place of the application window's logical tree so that it gets displayed. MVVM frameworks automate this procedure, but you can also do it manually as simply as this.
Your view would then bind to the logs collection to display each log, perhaps using a DataTemplate:
<ItemsControl ItemsSource="{Binding Logs}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<!-- XAML to display each Log does here -->
<TextBlock Text="{Binding FileName}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>

Answer 2

As an example, if you wanted that LogView being shown based on a button click in you main View.
public override void ShowCommandExecute()
{
var popup = new LogsView
{
WindowStartupLocation = WindowStartupLocation.CenterScreen,
DataContext = new LogsViewViewModel();
};
popup.ShowDialog();
}