Guidelines for Code style

Uno uses EditorConfig (here's our configuration) to maintain consistent coding styles and settings in our codebase, such as indent style, tab width, end of line characters, encoding, and more. Most IDEs should respect the EditorConfig settings by default when applying formatting. We typically observe the Microsoft C# Coding Conventions with one notable exception - Uno uses Tabs. If you install this Visual Studio plugin it will automatically format your contributions upon file save.

Refactoring

Pure refactoring for its own sake should generally be done in a separate, refactoring-only pull request, and you should generally open an issue to initiate discussion with the core team before you start such a refactoring, to determine if it's really appropriate. See this blog post on Open Source Contribution Etiquette for some explanation of the reasons why. Consistently-observed conventions are essential to the long-term health of the codebase.

Within a bugfix or enhancement PR, refactoring should be restricted to the relevant files, and it should respect the conventions of existing Uno code.

Patterns

This section describes some recurring patterns and practices you'll see in Uno code.

Partial classes

Partial class definitions are used extensively in Uno. The two main use cases for partial classes are platform-specific code and generated code.

However, in some cases where it makes sense, partial class files are also used for logical separation of code. If you're implementing a type that owns a lot of dependency properties, consider putting these in a separate partial, to avoid cluttering up the file where the actual business logic is with DP boilerplate. Another use case for a partial is a nested class with a large definition.

Disposables

Uno uses lightweight IDisposables widely for robust lifetime management. The most commonly used types for this purpose are SerialDisposable, CompositeDisposable, CancellationDisposable, and DisposableAction.

If you've used the Reactive Extensions framework, these names might be familiar, and in fact these disposables behave identically to their Rx equivalents. However, they've been transplanted into Uno, to avoid having to take a dependency on System.Reactive.

Extension methods

Extension methods are used throughout the Uno Platform codebase to add reusable functionality to existing types, particularly types coming from the Xamarin bindings. Extension methods should be defined in a dedicated class, with the naming convention [TypeName]Extensions.cs, where TypeName is the name of the type either being returned or passed as the this parameter.

A number of extensions to the standard .NET types already exists in Uno.Foundation. So, you should check those first to see if they do what you need.

When adding a new extension method class, it should typically be marked internal, to avoid naming clashes with existing consumer code.

Conventions

Braces

if (condition)
{
    // do something
}
else
{
    // use braces even for single line conditions
}

Integration Tests (UI Tests)

[ActivePlatforms(Platform.Android, Platform.Browser, Platform.iOS)]
[TestFixture]
public class LocalSettings_Tests : SampleControlUITestBase
{
    [Test]
    [AutoRetry]
    public void ClearAddContainsRemove()
    {
        // Navigate to this x:Class control name
        Run("UITests.Shared.Windows_Storage_ApplicationData.LocalSettings");

        // Define elements that will be interacted with at the start of the test
        var containerName = _app.Marked("ContainerName");
        var clearButton = _app.Marked("ClearButton");
        var addButton = _app.Marked("AddButton");
        var containsButton = _app.Marked("ContainsButton");
        var removeButton = _app.Marked("RemoveButton");
        var output = _app.Marked("Output");

        // Specify what user interface element to wait on before starting test execution
        _app.WaitForElement(clearButton);

        // Take an initial screenshot
        TakeScreenshot("Initial State");

        // Assert initial state
        Assert.AreEqual("Local", containerName.GetDependencyPropertyValue("Text")?.ToString());
        Assert.AreEqual(string.Empty, output.GetDependencyPropertyValue("Text")?.ToString());

        {
            _app.Tap(clearButton);
            _app.WaitForDependencyPropertyValue(output, "Text", 0);
            TakeScreenshot("Clear Button");
        }

        {
            _app.Tap(addButton);
           _app.WaitForDependencyPropertyValue(output, "Text", 1);
            TakeScreenshot("Add Button");
        }

        {
            _app.Tap(containsButton);
            _app.WaitForDependencyPropertyValue(output, "Text", "True");
            TakeScreenshot("Contains Button");
        }

        {
            _app.Tap(removeButton);
            _app.WaitForDependencyPropertyValue(output, "Text", 0);
            TakeScreenshot("Remove Button");
        }
    }
}