设置捕获设备EmguCV

我正在使用EmguCV的Capture类从网络摄像头拍摄图像。

根据类的文档(http://www.emgu.com/wiki/files/2.0.0.0/html/18b6eba7-f18b-fa87-8bf2-2acff68988cb.htm)， Capture有3个构造函数。

使用public Capture()应该使用默认相机，它工作正常。

正如我在其中一个例子中看到的，似乎

public Capture(string fileName) //takes a video file as the source for the captures.

最后一个构造函数是

public Capture(int camIndex) //which is supposed to "Create a capture using the specific camera" 

我尝试使用最后一个构造函数来允许用户选择设备，以防他有多个摄像头(例如，笔记本电脑中的集成摄像头或插入USB摄像头)

我的问题是我不知道如何获得可用设备的列表。尝试创建索引从0到99的捕获，并尝试捕获一个帧，期望出现异常，但它只捕获了100个黑色图像。此外，当我使用默认相机时，我不知道如何获得他的索引。

帮忙吗?

编辑:有了Shiva的答案中的信息，我得到了这个工作(我把它贴出来供将来参考):

private void onLoad(object sender, RoutedEventArgs e)
{
    //Add the image processing to the dispatcher
    this.Dispatcher.Hooks.DispatcherInactive += new EventHandler(dispatcherTimer_Tick);
    //Get the information about the installed cameras and add the combobox items 
    DsDevice[] _SystemCamereas = DsDevice.GetDevicesOfCat(FilterCategory.VideoInputDevice);
    Video_Device[] WebCams = new Video_Device[_SystemCamereas.Length];
    for (int i = 0; i < _SystemCamereas.Length; i++)
    {
        WebCams[i] = new Video_Device(i, _SystemCamereas[i].Name, _SystemCamereas[i].ClassID); //fill web cam array
        ComboBoxDevices.Items.Add(WebCams[i].ToString());
    }
}
private void dispatcherTimer_Tick(object sender, EventArgs e)
{
    if (capture != null)
    {
        //Capture an image
        Image<Bgr, byte> img = capture.QueryFrame();
        //Show the image in the window
        ImageOriginal.Source = ImageProcessor.ToBitmapSource(img);
    }
}
private void ComboBoxDevices_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    //If there is already a capture, dispose it
    if (capture != null)
    {
        capture.Dispose();
    }
    //Get the selected camera
    int selectedDevice = ComboBoxDevices.SelectedIndex;
    try
    {
        //Create new capture with the selected camera
        capture = new Capture(selectedDevice);
    }
    catch (Exception excpt)
    {
        MessageBox.Show(excpt.Message);
    }
}

 Capture grabber = new Emgu.CV.Capture(@".'..'..'file.avi");//can be relative path or absolute path of the video file.

    DsDevice[] _SystemCamereas = DsDevice.GetDevicesOfCat(FilterCategory.VideoInputDevice);
    Video_Device[] WebCams = new Video_Device[_SystemCamereas.Length];
        for (int i = 0; i < _SystemCamereas.Length; i++)
        {
            WebCams[i] = new Video_Device(i, _SystemCamereas[i].Name, _SystemCamereas[i].ClassID); //fill web cam array
            Camera_Selection.Items.Add(WebCams[i].ToString());
        }

Capture grabber = new Emgu.CV.Capture(0);