Development Experience(s)

Virtualbox getting stuck at 0% Got these errors when setting up my new environment - Warning! Unknown CPU features: 0x178ffe7f7859f - Warning! Unknown capability 0x1003 returning: 3f 38 00 00 00 00 00 00 ... with Virtualbox hanging at "Starting virtual machine ..." 0%. Fix As Administrator, run  bcdedit /set hypervisorlaunchtype off Background & references These errors were both indicative of Microsoft's Hypervisor running. When trying to shut it down, it indicated that the Container Manager Service was running despite the Containers feature being disabled. -  https://forums.virtualbox.org/viewtopic.php?f=6&t=92440 -  https://stackoverflow.com/questions/5482223/vt-x-is-not-available-when-i-start-my-virtual-machine Log sample 00:00:01.995347 NEM: Warning! Unknown CPU features: 0x178ffe7f7859f 00:00:01.995354 NEM: WHvCapabilityCodeProcessorClFlushSize = 2^8 00:00:01.996539 NEM: Warning! Unknown capability 0x1003 returning:

TL;DR In order to allow nullable reference types, upgrade your project to .NET Standard 2.1 which defaults to using C# 8.0. -  https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/configure-language-version Background An issue arose in our Team City build server, where JetBrains' inspectcode.exe  reported CSharpWarnings::CS8632 ( The annotation for nullable reference types should only be used in code within a '#nullable' annotations context ) although we'd enabled the nullable context in our .targets file and although Visual Studio didn't complain. After some digging around, we found that we were building against the .NET Standard 2.0 framework, whereas the C# 8 features that we were reaching for, requires .NET Standard 2.1. After an upgrade, inspectcode.exe happily accepted our nullable annotations and let our code through the rest of the build pipeline.