Microsoft has released version 8.0.0 of .NET Community Toolkit (NCT), a collection of helpers and APIs that make it easier to use patterns like MVVM (model-view-viewmodel) independently of the underlying platform. In this version, developers can benefit from reduced boilerplate code and streamlined API methods.
The sprawl of Microsoft UI frameworks in the last years (WPF, UWP, WinUI, Xamarin and MAUI) has made their .NET developers’ life harder if they wanted to build shared, platform-independent code in their applications. Microsoft and other developers in the community started sharing libraries and extensions for these frameworks in an effort to save developers’ time and reduce the implementation difficulty. Among other initiatives, a small MVVM library called MvvmLight developed by Laurent Bugnion saw significant adoption.
NCT is derived from a fork of Windows Community Toolkit (WCT) at version 7. WCT has extensions for WinUI and UWP, both being Windows-only frameworks. NCT inherits parts of code contributed to WCT that could be safely reused and it focuses on the platform-agnostic features that .NET application developers can benefit from. It includes a fast MVVM library that has been influenced by the design of MvvmLight. Microsoft mentions that NCT is used in their own developments such as Microsoft Store and Photos app.
Programming MVVM pattern leads involves creating commands and observable properties that drive UI updates. A basic command and observable property using NCT MVVM library looks like this:
Observable property Name
private string? name;
public string? Name
{
get => name;
set => SetProperty(ref name, value);
}
Command SayHello
private void SayHello()
{
Console.WriteLine("Hello");
}
private ICommand? sayHelloCommand;
public ICommand SayHelloCommand => sayHelloCommand ??= new RelayCommand(SayHello);
Version 8.0.0 of NCT simplifies this repetitive code by annotating properties and methods with attributes. These attributes get compiled, behind the scenes, into the code equivalent as the one seen before, using the Roslyn compiler source generator feature.
Observable property Name with annotations:
[ObservableProperty]
private string? name;
Command SayHello with annotations:
[RelayCommand]
private void SayHello()
{
Console.WriteLine("Hello");
}
Another source of boilerplate code in Microsoft MVVM frameworks is the implementation of the INotifyPropertyChanged interface. It signals to the client code that a property has changed in the model and that it should probably redraw the UI to reflect the change. The cumbersome syntax of notifications using INotifyPropertyChanged has prompted developers to create workarounds that encapsulate this behaviour as an abstraction, but as .NET doesn’t allow for multiple inheritance, the model class can’t inherit from any data parent class. NCT adds an annotation attribute that will generate the source code for this interface while still allowing the model to inherit from any other class, reducing the code verbosity.
A view model inheriting from a base type while still handling INotifyPropertyChanged behaviour
[INotifyPropertyChanged]
public partial class MyViewModel : SomeOtherType
{
}
This source generation feature of the new version has been hailed as a major improvement by some .NET developers.
Other NCT components that developers can use are helpers for parameter error validation or guard clauses. There is a set of helpers for leveraging high-performance .NET APIs such as Memory<T> and Span<T>. Microsoft recommends studying the source code of the MVVM sample application to get familiarised with the improvements in the new release.
Starting from version 8, the source code of all community toolkits is hosted under a single GitHub organisation under the umbrella of .NET Foundation. The NCT 8.0.0 is available as a NuGet package and it will run on any .NET Standard 2.0 platform, making it compatible with the legacy .NET Framework, but it will target the most recent .NET runtime to benefit from the performance improvements in them.