.NET 5 Known Issues

This document lists known issues for .NET 5 Preview 1 and beyond releases which may be encountered during usage.

.NET Runtime

Certain regular expressions involving negated character classes may fail to match correctly. This was a regression that occurred during extensive performance improvements made to the regular expression engine in 5.0. There is no general workaround, but modifying the expression may avoid the problem. This will be fixed in Preview 2. The issue dotnet/runtime #33399 explains the bug in detail.
Stepping with the debugger into code in certain assemblies in the .NET Platform may not succeed. This is because the assemblies do not have correct SourceLink information. This will be fixed in Preview 2. It is tracked by dotnet/runtime #33097.
The Microsoft.Windows.Compatibility package references dependencies that are not available at the targeted versions. To workaround, individually reference the packages your project needs. It is tracked by dotnet/runtime/issues #34351

The Microsoft.Windows.Compatibility package references dependencies that are not available at the targeted versions. To workaround, individually reference the packages your project needs. It is tracked by dotnet/runtime/issues #34351

When running a docker enabled application from Visual Studio or running dotnet dev-certs https --trust -ep <<path.pfx>> -p <<password>> the HTTPS certificate created by ASP.NET Core will become corrupted and will prevent applications from running. If you try to run the dotnet dev-certs tool again it will think that there is no valid certificate and will try to recreate a new one every time it runs. To avoid this situation, you can add a global.json file at the root of your project and set it to use the latest 3.1.xxx installed sdk. If you tried to run the application within Visual Studio and it corrupted the certificate you will have to clean the existing certificates from your certificate store using the windows tooling. To do that, open the certificate manager (Windows+R -> mmc -> File -> Add remote add-in -> Certificates -> Current user -> Personal) and delete all the certificates that contain the "ASP.NET Core HTTPS development certificate" and also remove them from Trusted Root Certification Authorities We recommend to not create / open any docker-enabled projects while on Preview 4 SDK.

This will be fixed in the Preview 5 release. It is tracked by dotnet/aspnetcore/issues #21733

Runtime-dependent deployments of apps targeting .NET Core 3.1 that are created with .NET Core SDK 5.0.100 Preview 1 will require version 3.1.2 of the .NET Core runtime. This issue is tracked by dotnet/sdk #10812