IRoutedCommandHandlerTCommand - интерфейс

public interface IRoutedCommandHandler<in TCommand> : IRoutedCommandHandler
where TCommand : IRoutedCommand

Public Interface IRoutedCommandHandler(Of In TCommand As IRoutedCommand)
	Inherits IRoutedCommandHandler

generic<typename TCommand>
where TCommand : IRoutedCommand
public interface class IRoutedCommandHandler : IRoutedCommandHandler

type IRoutedCommandHandler<'TCommand when 'TCommand : IRoutedCommand> =  
    interface
        interface IRoutedCommandHandler
    end