Upgrade to open-source framework for cross-platform .NET development adds drag-and-drop XAML designer and expands Windows Presentation Framework support. Credit: Shutterstock / Jacob Lund OpenSilver 3.1, the latest version of Userware’s open-source framework for cross-platform .NET development, has arrived with what the company calls the first-ever drag-and-drop XAML designer for Microsoft’s Visual Studio Code editor. Announced December 10, the OpenSilver 3.1 SDK can be downloaded from the project website. The XAML designer is described by Userware as a major milestone in cross-platform .NET development. Previously, XAML UI design was mostly limited to Visual Studio on Windows, leaving developers on macOS and Linux without visual design tools, the company said. OpenSilver 3.1 introduces a fully cross-platform designer, enabling developers to create user interfaces visually in VS Code on any operating system. The designer is available directly in VS Code; an online version is available at xaml.io. OpenSilver is perhaps best known as a replacement for Microsoft’s Silverlight rich Internet application framework. As part of Userware’s “WPF everywhere” strategy, OpenSilver 3.1 adds support for several Windows Presentation Framework features including DynamicResource, MultiBinding, x:Static, and UniformGrid. These features are intended to make it easier to build feature-rich applications with familiar WPF tools, Userware said. More WPF support is planned for mid-2025, with backing for features such as triggers and styles. Also new in OpenSilver 3.1 is a modern UI theme inspired by Material and Fluent Design principles. The theme provides a flat, contemporary aesthetic with built-in light and dark modes to help developers create visually appealing web applications, Userware said. Tools within the XAML designer enable adjustment of color palettes for branding. Fully compatible with .NET 9, OpenSilver 3.1 follows the July release of OpenSilver 3.0, which featured a generative AI-powered UI designer. OpenSilver applications run natively in modern browsers using HTML5 and WebAssembly. Future plans for OpenSilver call for full WPF compatibility, MAUI (Multi-platform App UI) capability for cross-platform apps, Blazor web framework interoperability, and 3D UI support. Microsoft .NETSoftware Development