WPF MVVM 更新后台工作线程上的视图模型

WPF MVVM 是一种常用的框架，用于开发 Windows Presentation Foundation (WPF) 应用程序。它将界面（视图）与后台逻辑（模型）分离，通过视图模型（ViewModel）来协调二者之间的交互。在使用 MVVM 模式时，我们经常需要在后台工作线程上更新视图模型。本文将介绍如何 ，并提供一个案例代码来演示这个过程。

csharp
public class TimerViewModel : INotifyPropertyChanged
{
    private TimeSpan _time;
    public TimeSpan Time
    {
        get { return _time; }
        set
        {
            if (_time != value)
            {
                _time = value;
                OnPropertyChanged(nameof(Time));
            }
        }
    }
    private bool _isRunning;
    public bool IsRunning
    {
        get { return _isRunning; }
        set
        {
            if (_isRunning != value)
            {
                _isRunning = value;
                OnPropertyChanged(nameof(IsRunning));
            }
        }
    }
    public ICommand StartCommand { get; }
    public ICommand PauseCommand { get; }
    public ICommand ResetCommand { get; }
    // 其他代码...
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

csharp
public class Timer
{
    private TimerViewModel _viewModel;
    private Thread _thread;
    private bool _isRunning;
    public Timer(TimerViewModel viewModel)
    {
        _viewModel = viewModel;
        _thread = new Thread(UpdateTimer);
        _isRunning = true;
    }
    public void Start()
    {
        _thread.Start();
        _viewModel.IsRunning = true;
    }
    public void Pause()
    {
        _isRunning = false;
        _viewModel.IsRunning = false;
    }
    public void Reset()
    {
        _viewModel.Time = TimeSpan.Zero;
    }
    private void UpdateTimer()
    {
        while (_isRunning)
        {
            Thread.Sleep(1000);
            _viewModel.Time = _viewModel.Time.Add(TimeSpan.FromSeconds(1));
        }
    }
}

csharp
private void UpdateTimer()
{
    while (_isRunning)
    {
        Thread.Sleep(1000);
        Application.Current.Dispatcher.Invoke(() =>
        {
            _viewModel.Time = _viewModel.Time.Add(TimeSpan.FromSeconds(1));
        });
    }
}