I've come up with something, I'm relatively happy with. This has saved me from creating 100s of composite ViewModel's and while it does introduce some unnecessary complexity it does dramatically reduce the amount copy/paste code I need to write.
VMFactoryViewModel.cs
public class CreatedViewModelEventArgs<T> : EventArgs where T : ViewModelBase
{
public T ViewModel { get; private set; }
public CreatedViewModelEventArgs(T viewModel)
{
ViewModel = viewModel;
}
}
public class VMFactoryViewModel<T> : ViewModelBase where T : ViewModelBase
{
private Func<string, T> _createViewModel;
private RelayCommand<string> _createViewModelCommand;
private readonly IDialogService _dialogService;
/// <summary>
/// Returns a command that creates the view model.
/// </summary>
public ICommand CreateViewModelCommand
{
get
{
if (_createViewModelCommand == null)
_createViewModelCommand = new RelayCommand<string>(x => CreateViewModel(x));
return _createViewModelCommand;
}
}
public event EventHandler<CreatedViewModelEventArgs<T>> CreatedViewModel;
private void OnCreatedViewModel(T viewModel)
{
var handler = CreatedViewModel;
if (handler != null)
handler(this, new CreatedViewModelEventArgs<T>(viewModel));
}
public VMFactoryViewModel(IDialogService dialogService, Func<string, T> createViewModel)
{
_dialogService = dialogService;
_createViewModel = createViewModel;
}
private void CreateViewModel(string viewModelId)
{
try
{
OnCreatedViewModel(_createViewModel(viewModelId));
}
catch (Exception ex)
{
_dialogService.Show(ex.Message);
}
}
}
VMFactoryUserControl.cs
public class VMFactoryUserControl<T> : UserControl where T : ViewModelBase
{
public static readonly DependencyProperty VMFactoryProperty = DependencyProperty.Register("VMFactory", typeof(VMFactoryViewModel<T>), typeof(VMFactoryUserControl<T>));
public VMFactoryViewModel<T> VMFactory
{
get { return (VMFactoryViewModel<T>)GetValue(VMFactoryProperty); }
set { SetValue(VMFactoryProperty, value); }
}
}
GenericView.xaml
<ctrl:VMFactoryUserControl x:Class="GenericProject.View.GenericView"
x:TypeArguments="vm:GenericViewModel"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:ctrl="clr-namespace:SomeProject.Controls;assembly=SomeProject.Controls"
xmlns:vm="clr-namespace:GenericProject.ViewModel">
<Grid>
<!-- Column Definitions -->
<!-- Row Definitions -->
<Label Grid.Row="0" Grid.Column="0" Content="Generic Id:" HorizontalAlignment="Right" />
<ctrl:CommandTextBox Grid.Row="0" Grid.Column="2"
Command="{Binding VMFactory.CreateViewModelCommand, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}"
CommandParameter="{Binding Text, RelativeSource={RelativeSource Self}}" />
<Label Grid.Row="0" Grid.Column="3" Content="Generic Property:" HorizontalAlignment="Right" />
<TextBox Grid.Row="0" Grid.Column="5" IsEnabled="False" Text="{Binding GenericProperty, Mode=OneWay}" />
<!--Additional Read Only Values-->
</Grid>
</ctrl:VMFactoryUserControl>
GenericView.xaml.cs
public partial class GenericView : VMFactoryUserControl<GenericViewModel>
{
public GenericView()
{
InitializeComponent();
}
}
MainPageViewModel.cs
public class MainPageViewModel : ViewModelBase
{
private readonly IDialogService _dialogService;
private GenericViewModel _generic;
private readonly VMFactoryViewModel<GenericViewModel> _genericFactory;
public GenericViewModel Generic
{
get { return _generic; }
private set
{
if (_generic != value)
{
_generic = value;
base.OnPropertyChanged("Generic");
}
}
}
public VMFactoryViewModel<GenericViewModel> GenericFactory
{
get { return _genericFactory; }
}
private void OnGenericFactoryCreatedViewModel(object sender, CreatedViewModelEventArgs<GenericViewModel> e)
{
Generic = e.ViewModel;
}
public MainPageViewModel(IDialogService dialogService)
{
_dialogService = dialogService;
_genericFactory = new VMFactoryViewModel<GenericViewModel>(_dialogService, x => new GenericViewModel(_dialogService, GetGeneric(x)));
_genericFactory.CreatedViewModel += OnGenericFactoryCreatedViewModel;
}
private Generic GetGeneric(string genericId)
{
// Return some Generic model.
}
}
MainPage.xaml
<Page x:Class="GenericProject.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vw="clr-namespace:GenericProject.View">
<StackPanel>
<!-- Headers and Additional Content. -->
<vw:EventView DataContext="{Binding Generic}"
VMFactory="{Binding DataContext.GenericFactory, RelativeSource={RelativeSource AncestorType={x:Type Page}}}" />
</StackPanel>
</Page>
