CommunityToolkit.Mvvm

 public class ViewModel : ObservableObject
    {
        public ViewModel()
        {
            ShowCommand = new RelayCommand<string>(Show);
        }
        private string name;
        public string Name
        {
            get { return name; }
            set
            {
                name = value;
                OnPropertyChanged();
            }
        }
        public RelayCommand<string> ShowCommand { get;  }


        public void Show(string content)
        {
            Name = "点击了按钮！";
            MessageBox.Show(content);
            //发送消息 给Token1的地址发送一个string类型的值 content
            WeakReferenceMessenger.Default.Send(content, "Token1");
        }

    }

<Grid>
        <StackPanel>
        <TextBox Text="{Binding Name}"/>
        <TextBox x:Name="txt" Width="200" Height="25"/>
        <Button Command="{Binding ShowCommand}"
               CommandParameter="{Binding ElementName=txt,Path=Text}" Width="50" Height="25">button</Button>
        </StackPanel>
    </Grid>

 public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = new ViewModel() { Name = "Hello!" };
            //注册一个接收string类型参数的消息，地址是：Token1
            WeakReferenceMessenger.Default.Register<string,string>(this, "Token1", Show);
        }
        public void Show(object recipient, string value)
        {
            MessageBox.Show($"来自Token1的消息:{value}");
        }


    }