ObservableCollection 更新列表

Question

我也是 WPF 和 MVVM 的新手。我正在我的程序中搜索 USB 设备。但是如果我连接了一个新的设备，需要重启程序才能显示。

怎么做，即刻刷新。

目前我在 class 中搜索设备：

public List<Devices> devices = new List<Devices>();

    public void FindDevices() // spremeni v public bool da dobis feedback 
    {


        _deviceList = HidDevices.Enumerate(VendorID, ProductID).ToArray();

...     devices.Add(new Devices()
            {
                DeviceId = nod + 1,
                ManufacturerId = deviceManufacturerstring[nod],
                ProductId = deviceProductstring[nod],
                SerialNumberId = deviceSNstring[nod],
                HardwareVersionId = "test4",
                FirmwareVersionId = "test5",
                DateOfManufaturedId = "test6"

            });

在循环中，我将设备添加到列表中。我需要循环，因为我从每个设备读取了一些数据。

我稍后将此设备添加到 ViewModel 的列表中：

public class Windows1ViewModel : ViewModelBase
{
    public ObservableCollection<Devices> devfuck { get; protected set; }
    List<Devices> _devicelist;

    public List<Devices> Devices
    {
        get { return _devicelist; }
        set { _devicelist = value; }
    }

    public Windows1ViewModel()
    {

        USBmiddleware cs = new USBmiddleware();
        cs.FindDevices();


        devfuck = new ObservableCollection<Devices>();


        foreach (var item in cs.devices)
        {
            devfuck.Add(item);
        }

        List<Devices> keks = cs.devices;



        NotifyPropertyChanged("devfuck");
    }


    public List<Devices> lvdevices
    {
        get { return _devicelist; }
        set { _devicelist = value; }
    }

要改变什么？在哪里添加 INotifyPropertyChanged？或者如何解决我的问题？请帮忙。谢谢！

我的 ViewModelBase

public class ViewModelBase : INotifyPropertyChanged, IDisposable
{


    protected ViewModelBase()
    {
    }



    #region DisplayName


    public virtual string DisplayName { get; protected set; }

    #endregion // DisplayName

    #region Debugging Aides


    [Conditional("DEBUG")]
    [DebuggerStepThrough]
    public void VerifyPropertyName(string propertyName)
    {
        // Verify that the property name matches a real,  
        // public, instance property on this object.
        if (TypeDescriptor.GetProperties(this)[propertyName] == null)
        {
            string msg = "Invalid property name: " + propertyName;

            if (this.ThrowOnInvalidPropertyName)
                throw new Exception(msg);
            else
                Debug.Fail(msg);
        }
    }


    protected virtual bool ThrowOnInvalidPropertyName { get; private set; }



    public event PropertyChangedEventHandler PropertyChanged;


    /// <param name="propertyName">The property that has a new value.</param>
    protected virtual void NotifyPropertyChanged(string propertyName)
    {
        this.VerifyPropertyName(propertyName);

        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
        {
            var e = new PropertyChangedEventArgs(propertyName);
            handler(this, e);
        }
    }

    protected virtual void NotifyPropertyChangedAll(object inOjbect)
    {
        foreach (PropertyInfo pi in inOjbect.GetType().GetProperties())
        {
            NotifyPropertyChanged(pi.Name);
        }
    }
    public virtual void Refresh()
    {
        NotifyPropertyChangedAll(this);
    }



    public void Dispose()
    {
        this.OnDispose();
    }

    /// <summary>
    /// Child classes can override this method to perform 
    /// clean-up logic, such as removing event handlers.
    /// </summary>
    protected virtual void OnDispose()
    {
    }



    ~ViewModelBase()
    {
        string msg = string.Format("{0} ({1}) ({2}) Finalized", this.GetType().Name, this.DisplayName, this.GetHashCode());
        System.Diagnostics.Debug.WriteLine(msg);
    }


}

Answer 1

您需要在 Windows1ViewModel class 中实施 INotifyPropertyChanged interface。然后你需要从你的属性 setter 调用它，或者在你设置属性之后调用它。

接下来，您应该设置一个 DispatcherTimer 来每隔一段时间调用您的 FindDevices 方法，然后从那里更新 ObservableCollection 属性。

Answer 2

您可以使用经常调用（根据需要）的计时器来完成此操作。当然，如果您可以使用事件管理来做到这一点，那就更性感了...

谢天谢地，有办法做到这一点：

var watcher = new ManagementEventWatcher();
var query = new WqlEventQuery("SELECT * FROM Win32_DeviceChangeEvent WHERE       EventType = 2");
watcher.EventArrived += new EventArrivedEventHandler(watcher_EventArrived);
watcher.Query = query;
watcher.Start();

如此处所述：Detecting USB drive insertion and removal using windows service and c#

然后您可以订阅该事件并调用您的

FindDevices()

从那里开始。

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