WPF: implement MVVM button command - wpf

Question

So i have WPF application with main windoes and 2 UserControls:
HomeView.xaml
OptionsView.xaml
View Model
public class ApplicationViewModel : INotifyPropertyChanged
{
#region Fields
private ICommand changePageCommand;
private ICommand addFilesCommand;
private IPageViewModel _currentPageViewModel;
private List<IPageViewModel> _pageViewModels;
#endregion
public ApplicationViewModel()
{
// Add available pages
PageViewModels.Add(new HomeViewModel() { IsSelected = true });
PageViewModels.Add(new OptionsViewModel() { IsSelected = false });
// Set starting page
CurrentPageViewModel = PageViewModels[0];
}
#region Properties / Commands
public ICommand ChangePageCommand
{
get
{
if (changePageCommand == null)
{
changePageCommand = new RelayCommand(
p => ChangeViewModel((IPageViewModel)p),
p => p is IPageViewModel);
}
return changePageCommand;
}
}
public List<IPageViewModel> PageViewModels
{
get
{
if (_pageViewModels == null)
_pageViewModels = new List<IPageViewModel>();
return _pageViewModels;
}
}
public IPageViewModel CurrentPageViewModel
{
get
{
return _currentPageViewModel;
}
set
{
if (_currentPageViewModel != value)
{
_currentPageViewModel = value;
OnPropertyChanged("CurrentPageViewModel");
}
}
}
#endregion
#region Methods
private void ChangeViewModel(IPageViewModel viewModel)
{
if (!PageViewModels.Contains(viewModel))
PageViewModels.Add(viewModel);
CurrentPageViewModel = PageViewModels.FirstOrDefault(vm => vm == viewModel);
}
#endregion
}
Whan application start
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
MainWindow app = new MainWindow();
ApplicationViewModel context = new ApplicationViewModel();
app.DataContext = context;
app.Show();
}
}
Windows respurces
<Window.Resources>
<DataTemplate DataType="{x:Type home:HomeViewModel}">
<home:HomeView />
</DataTemplate>
<DataTemplate DataType="{x:Type options:OptionsViewModel}">
<options:OptionsView />
</DataTemplate>
</Window.Resources>
And inside HomeView.xaml i have simple button:
<Button Command="{Binding DataContext.AddFilesCommand, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
CommandParameter="{Binding}"/>
And i want to add simple Click command, something.
So i try to add this ICommand:
public ICommand AddFilesCommand
{
}
Any suggestions how to add this kind on command that will execute after each Button Click ?

Answer 1

This can be done a lot easier. I would create a class to implement commands easily:
using System;
using System.Windows.Input;
namespace YourNameSpace
{
public class RelayCommand : ICommand
{
private Action Action;
public Command(Action _action)
{
Action = _action;
}
public event EventHandler CanExecuteChanged = (sender, e) => { };
public bool CanExecute(object parameter) => true;
public void Execute(object parameter)
{
Action();
}
}
}
Then create the command (you don't need private ICommand for this):
public ICommand AddFileCommand { get; set; }
And use it like this (in the constructor):
AddFileCommand = new RelayCommand(()=>
{
MethodToExecute();
});
XAML:
<Button Command="{Binding AddFileCommand}"/>
This way your code will be easier to see trough.