Friday, 2 October 2015

Detect USB drives in a WPF application



We can use the class System.IO.DriveInfo to retrieve all the drives on the system and look for drives where the DriveType is Removable. In addition, the removable drive (USB usually) must be ready, which is accessible as the property IsReady. First off, we define a provider to retrieve the removable drives:
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;

    namespace TestPopWpfWindow
    {

    public static class UsbDriveListProvider
    {


        public static IEnumerable<DriveInfo> GetAllRemovableDrives()
        {
            var driveInfos = DriveInfo.GetDrives().AsEnumerable();
            driveInfos = driveInfos.Where(drive => drive.DriveType == DriveType.Removable);
            return driveInfos;
        }

    }
}

Let us use the MVVM pattern also, so we define a ViewModelbase class, implementing INotifyPropertyChanged.
using System.ComponentModel;

namespace TestPopWpfWindow
{

    public class ViewModelBase : INotifyPropertyChanged
    {

        public event PropertyChangedEventHandler PropertyChanged;

        public void RaisePropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }


    }
}
It is also handy to have an implemetation of ICommand:
    using System;
    using System.Windows.Input;

    namespace TestPopWpfWindow
    {

        public class RelayCommand : ICommand
        {

            private Predicate<object> _canExecute;

            private Action<object> _execute;  


            public RelayCommand(Predicate<object> canExecute, Action<object> execute)
            {
                _canExecute = canExecute;
                _execute = execute;
            }

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

            public event EventHandler CanExecuteChanged;

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

        }
    }

We also set the DataContext of MainWindow to an instance of a demo view model defined afterwards:
namespace TestPopWpfWindow
{

    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
            DataContext = new UsbDriveInfoDemoViewModel();
        }

    }
}

We then define the view model itself and use System.Management.ManagementEventWatcher to look for changes in the drives mounted onto the system.
  using System;
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.IO;
    using System.Management;
    using System.Windows;
    using System.Windows.Input;

    namespace TestPopWpfWindow
    {

        public class UsbDriveInfoDemoViewModel : ViewModelBase, IDisposable
        {

            public UsbDriveInfoDemoViewModel()
            {
                DriveInfos = new List<DriveInfo>();
                ReloadDriveInfos();
                RegisterManagementEventWatching(); 
                TargetUsbDrive = @"E:<"; 
                AccessCommand = new RelayCommand(x => true, x => MessageBox.Show("Functionality executed."));
            }

            public int UsbDriveCount { get; set; }

            private string _targetUsbDrive;

            public string TargetUsbDrive
            {
                get { return _targetUsbDrive; }
                set
                {
                    if (_targetUsbDrive != value)
                    {
                        _targetUsbDrive = value; 
                        RaisePropertyChanged("TargetUsbDrive");
                        RaisePropertyChanged("DriveInfo");
                    }
                }
            }

            public ICommand AccessCommand { get; set; }

            private void ReloadDriveInfos()
            {
                var usbDrives = UsbDriveListProvider.GetAllRemovableDrives();

                Application.Current.Dispatcher.Invoke(() =>
                {
                    DriveInfos.Clear();

                    foreach (var usbDrive in usbDrives)
                    {
                        DriveInfos.Add(usbDrive);
                    }
                    UsbDriveCount = DriveInfos.Count;
                    RaisePropertyChanged("UsbDriveCount");
                    RaisePropertyChanged("DriveInfos");
                }); 
            }

            public List<DriveInfo> DriveInfos { get; set; }

            private ManagementEventWatcher _watcher;

            private void RegisterManagementEventWatching()
            {
                _watcher = new ManagementEventWatcher();
                var query = new WqlEventQuery("SELECT * FROM Win32_VolumeChangeEvent");
                _watcher.EventArrived += watcher_EventArrived;
                _watcher.Query = query;
                _watcher.Start();
            }

            private void watcher_EventArrived(object sender, EventArrivedEventArgs e)
            {
                Debug.WriteLine(e.NewEvent);
                ReloadDriveInfos();
            }



            public void Dispose()
            {
                if (_watcher != null)
                {
                    _watcher.Stop();
                    _watcher.EventArrived -= watcher_EventArrived;
                }
            }

        }

    }

We also define a WPF multi-converter next to enable the button:
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Windows.Data;

namespace TestPopWpfWindow
{

    public class UsbDriveAvailableEnablerConverter : IMultiValueConverter
    {

        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (values == null || values.Count() != 2)
                return false;

            var driveInfos = values[1] as List<DriveInfo>;
            var targetDrive = values[0] as string; 
            if (driveInfos == null || !driveInfos.Any() || string.IsNullOrEmpty(targetDrive))
                return false;
            return driveInfos.Any(d => d.IsReady && d.Name == targetDrive);
        }




        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

And we define a GUI to test this code:
<Window x:Class="TestPopWpfWindow.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:TestPopWpfWindow"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>

        <Style x:Key="usbLabel" TargetType="Label">
            <Style.Triggers>
                <DataTrigger Binding="{Binding IsReady}" Value="False">
                    <Setter Property="Background" Value="Gray"></Setter>
                </DataTrigger>
                <DataTrigger Binding="{Binding IsReady}" Value="True">
                    <Setter Property="Background" Value="Green"></Setter>
                </DataTrigger>
            </Style.Triggers>
        </Style>

        <local:UsbDriveAvailableEnablerConverter x:Key="usbDriveAvailableEnablerConverter"></local:UsbDriveAvailableEnablerConverter>

    </Window.Resources>


    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>

        </Grid.RowDefinitions>

        <StackPanel Orientation="Vertical">
            <TextBlock Text="USB Drive-detector" FontWeight="DemiBold" HorizontalAlignment="Center" FontSize="14" Margin="2"></TextBlock>
            <TextBlock Text="Removable drives on the system" FontWeight="Normal" HorizontalAlignment="Center" Margin="2"></TextBlock>
            <TextBlock Text="Drives detected:" FontWeight="Normal" HorizontalAlignment="Center" Margin="2"></TextBlock>
            <TextBlock Text="{Binding UsbDriveCount, UpdateSourceTrigger=PropertyChanged}" FontWeight="Normal" HorizontalAlignment="Center" Margin="2"></TextBlock>

            <ItemsControl Grid.Row="0" ItemsSource="{Binding DriveInfos, UpdateSourceTrigger=PropertyChanged}"
                          Width="100" BorderBrush="Black" BorderThickness="1">
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Vertical">
                            <Label Style="{StaticResource usbLabel}" Width="32" Height="32" FontSize="18" Foreground="White" Content="{Binding Name}">
                            </Label>
                        </StackPanel>

                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </StackPanel>

        <Button Grid.Row="1" Height="24" Width="130" VerticalAlignment="Top" Margin="10" Content="Access functionality" Command="{Binding AccessCommand}">
            <Button.IsEnabled>
                <MultiBinding Converter="{StaticResource usbDriveAvailableEnablerConverter}">
                    <MultiBinding.Bindings>
                        <Binding Path="TargetUsbDrive"></Binding>
                        <Binding Path="DriveInfos"></Binding>
                    </MultiBinding.Bindings>
                </MultiBinding>
            </Button.IsEnabled>
        </Button>

        <StackPanel Grid.Row="2" Orientation="Horizontal" HorizontalAlignment="Center">
            <TextBlock Margin="2" Text="Target this USB-drive:"></TextBlock>
            <TextBox Margin="2" Text="{Binding TargetUsbDrive, UpdateSourceTrigger=LostFocus}" Width="100"></TextBox>
        </StackPanel>

    </Grid>

</Window>

I have now provided the Visual Studio 2013 solution with the code above available for download here:

Download VS 2013 Solution with source code above

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