The latest version of OpenSilver 3.1, a remake of Microsoft's retired Silverlight web application framework, extends the visual designer launched in July to non-Windows platforms. It also includes support for .NET 9 and some WPF-specific features.
OpenSilver was launched in October 2021 by a French company, Userware. It is an open-source, MIT-licensed reimplementation of Silverlight. OpenSilver compiles .NET and XAML code into HTML5 and WebAssembly, reimplementing standard and selected third-party controls. It allows developers to reuse their legacy Silverlight or XAML applications instead of rewriting them. The latest update to OpenSilver was version 3.0 in July 2024, with the introduction of the visual, drag-and-drop XAML designer for Visual Studio.
The new designer is available as a Visual Studio Code extension, bringing full designer support on macOS and Linux platforms. It supports over a hundred controls and features an AI assistant for UI creation. The AI assistant requires a Microsoft account to be used.
OpenSilver 3.1 XAML designer running in VS Code on macOS (source: Userware)
Together with the cross-platform compatibility of the visual designer, there have been some changes in the OpenSilver platform. The most important one is the full support for the recently released .NET 9.
Until now, OpenSilver has mimicked the look and feel of the original Silverlight applications and controls. With this release, developers can choose between the "classic" theme and a modern one, with flat controls and bright primary colours. The modern theme comes in Light and Dark versions.
OpenSilver 3.1 Modern UI Theme (source: Userware)
OpenSilver already had a decent coverage of WPF code. As Silverlight was derived from WPF, there were some WPF-specific features that weren't supported in Silverlight (nor OpenSilver). In version 3.1, several of those features were implemented. Right now, UniformGrid, x:Static attribute, MultiBinding class and DynamicResource markup extension are supported.
On the Reddit dotnet community, the release video post of OpenSilver 3.1 triggered many comments, mostly about the fast pace and effects of the video. However, the comments regarding OpenSilver and the XAML designer are generally positive,
Userware plans to expand the capabilities of OpenSilver with several upcoming features: full WPF compatibility, MAUI integration, Blazor components interoperability and a full 3D support for their XRSharp.io framework.
The OpenSilver source code is available on GitHub. The repository containing OpenSilver has 1006 stars and has been forked 117 times. Beyond the Userware developer team, there are other active contributions to the project, with a total of 47 contributors. According to the OpenSilver website, companies that rely on this framework include Bayer, TATA, KPMG, and others.
