nkristek/smaragd

A platform-independent, lightweight library for developing .NET applications using the MVVM architecture

This is a very lightweight library containing base classes for implementing .NET applications using the MVVM architecture. It is fully unit tested and platform independent.

Features

Smaragd offers base implementations of key .NET interfaces for building WPF / MVVM applications.

In addition, it enables developers to:

• Build dialog and tree structures via DialogModel and TreeViewModel
• Execute commands synchronously and asynchronously via ViewModelCommand and AsyncViewModelCommand
• Perform validation via FuncValidation and PredicateValidation
• Manage state updates for interdependent properties via PropertySourceAttribute

For more information, please visit the documentation.

Installation

The recommended way to use this library is via NuGet.

Currently supported frameworks:

• .NET Standard 2.0 or higher
• .NET Framework 4.5 or higher

Quick Start

The following is a simple demonstration of some core features of Smaragd.

1. Choose a base class for your ViewModel.

   • Inherit from ViewModel if you want to use the fill feature set (recommended)
   • Inherit from Bindable if you only want an implementation of INotifyPropertyChanged and INotifyPropertyChanging

   class AppViewModel : ViewModel
   {
       // ...
   }

2. Add a property with a backing field that invokes PropertyChanged when set.

   class AppViewModel : ViewModel
   {
           private string _name;
           public string Name
           {
               get => _name;
               set => SetProperty(ref _name, value);
           }
   }

3. Make the property dependent on the ViewModel's IsDirty property. IsDirty indicates whether property values have changed. The Name property then automatically updates observing views when IsDirty changes.

   class AppViewModel : ViewModel
   {
           private string _name;
   
           [PropertySource(nameof(IsDirty))]
           public string Name
           {
               get => IsDirty ? $"{_name} (unsaved changes)" : _name;
               set => SetProperty(ref _name, value);
           }
   }

4. Add an async command to reset the IsDirty flag.

   class AppViewModel : ViewModel
   {
       private string _name;
   
       [PropertySource(nameof(IsDirty))]
       public string Name
       {
           get => IsDirty ? $"{_name} (unsaved changes)" : _name;
           set => SetProperty(ref _name, value);
       }
   
   
       private IViewModelCommand<AppViewModel> _saveCommand;
   
       [IsDirtyIgnored]
       [IsReadOnlyIgnored]
       public IViewModelCommand<AppViewModel> SaveCommand => _saveCommand ??= new SaveCommand(this)
   }
   
   
   class SaveCommand : AsyncViewModelCommand<AppViewModel>
   {
       public SaveCommand(AppViewModel context)
       {
           Context = context;
       }
   
       protected override async Task ExecuteAsync(AppViewModel viewModel, object parameter)
       {
           // SaveChanges(viewModel);
           viewModel.IsDirty = false;
       }
   }

5. Create a view in XAML for your ViewModel and enjoy working with bindings.

   <Window Title="{Binding Name}">
       <Button Command="{Binding SaveCommand}">
   </Window>

In case you would like to see a more advanced reference application please don't hesitate to visit my other project Stein.

Why another MVVM library?

This library originated in my other project Stein and was subsequently moved to its own repository and nuget package. The goal is to provide a great yet minimal foundation which also promotes a good code style. Nearly everything is marked virtual (except events) so you can customize it to fit your needs.

And of course, this library is 🚀blazing fast🚀.

Contribution

If you find a bug feel free to open an issue. Contributions are also appreciated.

smaragd's Issues

Having multiple INotifyCollectionChanged properties pointing to the same value will result in the PropertySourceAttribute not working correctly

private ObservableCollection<int> Values;

public ObservableCollection<int> Values1 => Values;

public ObservableCollection<int> Values2 => Values;

[PropertySource(nameof(Values1), NotifyCollectionChangedAction.Add, NotifyCollectionChangedAction.Remove, NotifyCollectionChangedAction.Replace, NotifyCollectionChangedAction.Reset)]
public int MinValue => Values1.Min();

[PropertySource(nameof(Values2), NotifyCollectionChangedAction.Add, NotifyCollectionChangedAction.Remove, NotifyCollectionChangedAction.Replace, NotifyCollectionChangedAction.Reset)]
public int MaxValue => Values2.Max();

This will result in either the PropertySourceAttribute from MinValue or MaxValue not working.

Improve TreeViewModel.Children collection

It should be improved, how child TreeViewModel's get added to the TreeViewModel.Children collection.

Change the project to .NET Standard

This would enable other .NET platforms like UWP applications to use this library. Currently it is a .NET Framework library.