这个例子是没有道理的，我只是在练习。

我有以下命令：

        public class NewCommand : ICommand
        {
            public event EventHandler CanExecuteChanged
            {
                add { CommandManager.RequerySuggested += value; }
                remove { CommandManager.RequerySuggested -= value; }
            }

            public bool CanExecute(object parameter)
            {
                return !((string)parameter == "sample");
            }

            public void Execute(object parameter)
            {
                MessageBox.Show("The New command was invoked");
            }
        }

，并且效果很好（按Button打开消息框），除了在string中更改TextBox不会执行任何操作。当Button应该被阻止时，不是。

这是我的XAML和ViewModel：

    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
        <TextBox Text="{Binding TextB}"></TextBox>
        <Button Command="{Binding Path=NewCommand}" FontSize="128">New</Button>
    </StackPanel>

public class ViewModel : INotifyPropertyChanged
        {
            private string _textB;
            public ICommand NewCommand { get; set; }
            public string TextB
            {
                get => _textB;
                set
                {
                    if (_textB == value) return;
                    _textB = value;
                    OnPropertyChanged(nameof(TextB));
                }
            }

            public event PropertyChangedEventHandler PropertyChanged;

            public void OnPropertyChanged(string memberName)
            {
                PropertyChanged?.Invoke(this,new PropertyChangedEventArgs(memberName));
            }
        }