'StringBuilder' does not contain a definition for 'AppendJoin' and no accessible extension method 'AppendJoin' accepting a first argument of type 'StringBuilder' could be found (are you missing a using directive or an assembly reference?)

Argument 1: cannot convert from 'char' to 'string'

Process completed with exit code 1.

The target framework 'netcoreapp3.1' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.

The target framework 'netcoreapp3.1' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.

The target framework 'netcoreapp3.1' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.

The target framework 'netcoreapp3.1' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.

The target framework 'netcoreapp3.1' is out of support and will not receive security updates in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy.