When you upgrade your .Net Core project to .Net 6, you are mostly likely going to run into following error.The feature 'global using directive' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
This happens due to a new feature introduced in C# 10.0. When you have a big project, all files a lot of using statements that refer to same namespaces. C# 10.0 allows you to create an implicit global reference to common namespaces. You can read more about it on Microsoft's documentation on following page.
As of this writing, .Net 6 is still in preview mode. When you upgrade your project, Visual Studio automatically tries to create these implicit global namespace references. This will also require that you have use the preview version of SDK in your project. If you are not ready for it yet, then add the following section in your project file. This will stop Visual Studio from automatically generating global reference file.
<PropertyGroup> <DisableImplicitNamespaceImports>true</DisableImplicitNamespaceImports> </PropertyGroup>