Hi Christian,
In MATLAB R2025a, the .NET Framework is automatically loaded as soon as MATLAB starts, which is a change from previous versions. This means that when you try to use the dotnetenv function to change the .NET environment, MATLAB gives an error because the .NET runtime is already loaded and cannot be reconfigured in the current session. Restarting MATLAB does not resolve the issue, as the framework is loaded immediately upon launch—often due to internal MathWorks components or installed toolboxes that require .NET. Unfortunately, in recent MATLAB versions, there is no supported way to fully prevent .NET from loading at startup. The best approach is to check for any custom startup scripts or third-party toolboxes that might trigger .NET loading, but even with these removed, core MATLAB components may still load .NET automatically. For users who need precise control over the .NET environment, the only effective solution is to contact MathWorks support and explain the workflow, as this is a known limitation in newer MATLAB releases.
