Recently I installed Visual Studio 2022 Preview to check new features of C# 13. But when I open my previous projects and try to check out new features like new lock object, I get this error:
The type or namespace name ‘Lock’ does not exist in the namespace ‘System.Threading’ (are you missing an assembly reference?)
I tried reopening and copying exact examples from Microsoft documentation, but still I get error.
>Solution :
If you open previous projects, their target framework are still on previous .NET you chose for those projects while creating them.
Go to: Project > ProjectProperties > Target framework
Choose the desired target framework.
Since you want to work with C# 13.0 features, you need to set to .NET 9.0 to be able to work with them.
Remember while making new projects, if you want to use new features of C# 13.0 and .NET 9, you should choose .NET 9.0 too.