Passing a string property to a command via a button CommandParameter in .NET 6

<Button [...] Command="{Binding PerformSearch}" CommandParameter="{Binding SearchString}" />

    internal class SearchCommand : ICommand
    {
        public event EventHandler? CanExecuteChanged;

        public bool CanExecute(object? parameter)
        {
            System.Diagnostics.Debug.WriteLine("CanExecute(parameter) : parameter=" + parameter);
            return true;
        }

        public void Execute(object? parameter)
        {
            System.Diagnostics.Debug.WriteLine("Execute(parameter) : parameter=" + parameter);
        }
    }
    //...
    internal class MainViewModel : INotifyPropertyChanged
    {
        // ...
        public ICommand? PerformSearch { get; } = new SearchCommand();
        // ...
    }

CanExecute(parameter) : parameter=
Execute(parameter) : parameter=

<Button [...] Command="{Binding PerformSearch}" CommandParameter="Hello" />

CanExecute(parameter) : parameter=Hello
Execute(parameter) : parameter=Hello