c# - 将 Silverlight 转换为 MVVM，几个问题

Question

我有一个正在转换为 MVVM 的 Silverlight 项目。这是我第一次使用这种模式，我正在努力解决一些问题。

所以基本上我在页面后面的 XAML 代码中有这个:

 OpenFileDialog ofd = new OpenFileDialog();
            if ((bool)ofd.ShowDialog())
            {
                _fileName = ofd.File.Name;
                FileStream fs = ofd.File.OpenRead();
                fileSize = (double)fs.Length;
                txtFileName.Text = fileName;
                index = 0;
                sendData = 0;

                byte[] file = new byte[fs.Length];
                fs.Read(file, 0, file.Length);
                //convertToChunks(file);

                prgUpload.Maximum = fileChunks.Count;
                prgUpload.Value = 0;
                //uploadChunks(index);
            }

而且我无法弄清楚如何将其连接起来以便能够在模型中使用它？我假设 View 模型开始发挥作用，但没有任何效果。

有什么想法吗？

这是正在进行的 XAML 工作:

<Grid x:Name="LayoutRoot" Width="475" Height="340">
    <Canvas Margin="8,8,0,0" Background="White" Height="320" VerticalAlignment="Top" HorizontalAlignment="Left" Width="475">
        <Button Width="75" Canvas.Left="380" Canvas.Top="43" Content="Browse" x:Name="btnBrowse" />
        <TextBox Canvas.Left="25" IsReadOnly="True"  Canvas.Top="43" TextWrapping="Wrap" Width="350" Text="{Binding Path=FileUploadName}" x:Name="txtFileName" />
        <ProgressBar Height="10" Width="350" Canvas.Left="25" Canvas.Top="99" x:Name="prgUpload" />

        <my:Label Content="Please select a file to upload"  Name="lblError" Canvas.Left="25" Canvas.Top="23" RenderTransformOrigin="0.133,-0.063" Width="220"/>
        <my:Label x:Name="lblProgress" Canvas.Left="25" Canvas.Top="78" RenderTransformOrigin="0.133,-0.063" Width="220"/>
    </Canvas>
</Grid>

基本上我希望它在用户选择要上传的文件后触发。

Answer 1

如果您想触发命令，这将为您完成工作

<Button Width="75" Canvas.Left="380" Canvas.Top="43" Content="Browse" x:Name="btnBrowse" 
  Command={Binding OpenFileCommand} />

例如，在构造函数后面的代码中

partial class MainWindow
{
   public MainWindow()
   {
     InitializeComponent();
     this.DataContext=new MainViewModel();
   }
}

在你的 ViewModel

   public ICommand OpenFileCommand { get; set; }

   public MainViewModel()
   {
       OpenFileCommand = new RelayCommand(OpenDialog) { IsEnabled = true };

   }

   private void OpenDialog()
   {
       OpenFileDialog ofd = new OpenFileDialog();
       if ((bool)ofd.ShowDialog())
       {
           _fileName = ofd.File.Name;
           FileStream fs = ofd.File.OpenRead();
           fileSize = (double)fs.Length;
           //txtFileName.Text = fileName;// Apply Binding 
           index = 0;
           sendData = 0;

           byte[] file = new byte[fs.Length];
           fs.Read(file, 0, file.Length);
           //convertToChunks(file);

           prgUpload.Maximum = fileChunks.Count;
           prgUpload.Value = 0;
           //uploadChunks(index);
       }
   }

和 RelayCommand

public class RelayCommand:ICommand
{
   private bool _isEnabled;
   public bool IsEnabled
   {
       get { return _isEnabled; }
       set
       {
           if (value != _isEnabled)
           {
               _isEnabled = value;
               if (CanExecuteChanged != null)
               {
                   CanExecuteChanged(this, EventArgs.Empty);
               }
           }
       }
   }
   private Action _handler;
   public RelayCommand(Action handler)
   {
       _handler = handler;
   }


   public bool CanExecute(object parameter)
   {
       return IsEnabled;
   }

   public event EventHandler CanExecuteChanged;

   public void Execute(object parameter)
   {
       _handler();
   }
}

为了在文本框中获取文件名，您必须将文本框绑定(bind)到 View 模型。这样它就会出现在 UI 上并实现 INotifyPropertyChanged。也看看这个会有帮助 Silverlight MVVM