Earlier this year we introduced SLNX, an XML-based solution file format that replaces the old, proprietary .sln layout with a much more concise, readable XML representation. It preserves the same solution data by folding common defaults into the format so files are smaller and easier to inspect and merge while retaining full build behavior. Tooling support is already available in Visual Studio and the dotnet CLI, however, our plan is to make this the default experience for Visual Studio 2026 forward.
One legitimate complaint is that the format does not inherently support ordering, more specifically, you could not define the start up project (you can in Visual Studio but it gets saved in your personal .suo file).
The immediate fix we applied is deliberately simple and explicit: add a DefaultStartup="true" attribute to the project element you want to launch first.
<Solution> <Project DefaultStartup="true" Path="ConsoleApp1/ConsoleApp1.csproj" /> <Project Path="SomeTestSolution/SomeTestSolution.csproj" /> </Solution>
That attribute is applied by the solution model at load time so Visual Studio treats that project as the default startup on first open, while existing .suo state continues to take precedence for individual developer environments.
