WPF数据绑定ProgressBar

Question

我正在制作WebClient用于下载文件的WPF应用程序。我想ProgressPercentage在ProgressBar控制器中显示。我在WebClient用于下载文件的类中有一个方法。我的问题是如何将绑定ProgressBar到e.ProgressPercentage。

类中的方法（DownloadFile）：

public async Task DownloadProtocol(string address, string location)
{

        Uri Uri = new Uri(address);
        using (WebClient client = new WebClient())
        {
            //client.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
            //client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgress);
            client.DownloadProgressChanged += (o, e) =>
            {
                Console.WriteLine(e.BytesReceived + " " + e.ProgressPercentage);
                //ProgressBar = e.ProgressPercentage???
            };

            client.DownloadFileCompleted += (o, e) =>
            {
                if (e.Cancelled == true)
                {
                    Console.WriteLine("Download has been canceled.");
                }
                else
                {

                    Console.WriteLine("Download completed!");
                }

            };

            await client.DownloadFileTaskAsync(Uri, location);
        }

}

进度条：

<ProgressBar HorizontalAlignment="Left" Height="24" Margin="130,127,0,0" VerticalAlignment="Top" Width="249"/>

Answer 1

对于一个干净的解决方案，您需要一个ViewModel类，我们在其中创建一个StartDownload方法，您可以通过单击Command或button单击来调用它window。

另一方面，有一个好Type名字IProgress<T>。它可以作为一个线人给我们，你可以用它类似于下面的示例播放;）

在DownloadViewModel.cs内部：

public sealed class DownloadViewModel : INotifyPropertyChanged
{
    private readonly IProgress<double> _progress;
    private double _progressValue;

    public double ProgressValue
    {
        get
        {
            return _progressValue;
        }
        set
        {
            _progressValue = value;
            OnPropertyChanged();
        }
    }

    public DownloadViewModel()
    {
        _progress = new Progress<double>(ProgressValueChanged);
    }

    private void ProgressValueChanged(double d)
    {
        ProgressValue = d;
    }

    public async void StartDownload(string address, string location)
    {
        await new MyDlClass().DownloadProtocol(_progress, address, location);
    }

    //-----------------------------------------------------------------------
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        var handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }
}

在MyDlClass内部。cs

public class MyDlClass
{
    public async Task DownloadProtocol(IProgress<double> progress, string address, string location)
    {

        Uri Uri = new Uri(address);
        using (WebClient client = new WebClient())
        {
            //client.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
            //client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgress);
            client.DownloadProgressChanged += (o, e) =>
            {
                Console.WriteLine(e.BytesReceived + " " + e.ProgressPercentage);
                progress.Report(e.ProgressPercentage);
            };

            client.DownloadFileCompleted += (o, e) =>
            {
                if (e.Cancelled == true)
                {
                    Console.WriteLine("Download has been canceled.");
                }
                else
                {

                    Console.WriteLine("Download completed!");
                }

            };

            await client.DownloadFileTaskAsync(Uri, location);
        }

    }
}

内部MyWindow.Xaml.cs和MyWindow.Xaml：

现在，您应该DataContext使用DownloadViewModel类的实例（通过Xaml或Code-Behind）填充窗口。

绑定到类的ProgressValue属性DownloadViewModel.cs：

<ProgressBar HorizontalAlignment="Left" Height="24" Margin="130,127,0,0" VerticalAlignment="Top" Width="249"
             Minimum="0"
             Maximum="100"
             Value="{Binding Path=ProgressValue}"/>

最后，在您的按钮OnClick中输入：

if(this.DataContext!=null)
   ((DownloadViewModel)this.DataContext).StartDownload("__@Address__","__@Location__");
else
    MessageBox.Show("DataContext is Null!");

结果：