Including partial views when applying the Mode-View-ViewModel design pattern
- by Filip Ekberg
Consider that I have an application that just handles Messages and Users I want my Window to have a common Menu and an area where the current View is displayed.
I can only work with either Messages or Users so I cannot work simultaniously with both Views. Therefore I have the following Controls
MessageView.xaml
UserView.xaml
Just to make it a bit easier, both the Message Model and the User Model looks like this:
Name
Description
Now, I have the following three ViewModels:
MainWindowViewModel
UsersViewModel
MessagesViewModel
The UsersViewModel and the MessagesViewModel both just fetch an ObserverableCollection<T> of its regarding Model which is bound in the corresponding View like this:
<DataGrid ItemSource="{Binding ModelCollection}" />
The MainWindowViewModel hooks up two different Commands that have implemented ICommand that looks something like the following:
public class ShowMessagesCommand : ICommand
{
private ViewModelBase ViewModel { get; set; }
public ShowMessagesCommand (ViewModelBase viewModel)
{
ViewModel = viewModel;
}
public void Execute(object parameter)
{
var viewModel = new ProductsViewModel();
ViewModel.PartialViewModel = new MessageView { DataContext = viewModel };
}
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
}
And there is another one a like it that will show Users. Now this introduced ViewModelBase which only holds the following:
public UIElement PartialViewModel
{
get { return (UIElement)GetValue(PartialViewModelProperty); }
set { SetValue(PartialViewModelProperty, value); }
}
public static readonly DependencyProperty PartialViewModelProperty =
DependencyProperty.Register("PartialViewModel", typeof(UIElement), typeof(ViewModelBase), new UIPropertyMetadata(null));
This dependency property is used in the MainWindow.xaml to display the User Control dynamicly like this:
<UserControl Content="{Binding PartialViewModel}" />
There are also two buttons on this Window that fires the Commands:
ShowMessagesCommand
ShowUsersCommand
And when these are fired, the UserControl changes because PartialViewModel is a dependency property.
I want to know if this is bad practice? Should I not inject the User Control like this? Is there another "better" alternative that corresponds better with the design pattern? Or is this a nice way of including partial views?
