WPF MVVM Toolkit add new button with command

gistfile1.cs

in xaml
        <Button Content="Generate key" Command="{Binding GenerateKeyCommand}"/>

in viewmodel
    private RelayCommand generateKeyCommand;
    public ICommand GenerateKeyCommand => generateKeyCommand ??= new RelayCommand(GenerateKey);

    private void GenerateKey()
    {
        MessageBox.Show("GenerateKey");
    }