VintaSoft Twain .NET SDK v10.2
Vintasoft.Twain Namespace / Device Class / AsyncEvents Property
Example




In This Topic
    AsyncEvents Property (Device)
    In This Topic
    Gets or sets an array with asynchronous events which the application wants the device to report.
    Syntax
    'Declaration
     
    Public Property AsyncEvents As DeviceEventId()
    'Usage
     
    Dim instance As Device
    Dim value() As DeviceEventId
     
    instance.AsyncEvents = value
     
    value = instance.AsyncEvents
    public DeviceEventId[] AsyncEvents {get; set;}
    public: __property DeviceEventId[]* get_AsyncEvents();
    public: __property void set_AsyncEvents( 
       DeviceEventId[]* value
    );
    public:
    property array<DeviceEventId>^ AsyncEvents {
       array<DeviceEventId>^ get();
       void set (    array<DeviceEventId>^ value);
    }
    Exceptions
    ExceptionDescription
    Thrown if device is in wrong state.
    Thrown if device does not support capability.
    Thrown if the .NET debugger is used and the function evaluation requires all threads to run.
    Remarks
    Call this property only when device is opened (State == DeviceState.Opened).

    Supported events IDs can be received by the GetSupportedAsyncEvents method.
    Example
    This example shows how to detect when paper is jammed.
    ''' <summary>
    ''' Detects the paper jamm.
    ''' </summary>
    Public Sub DetectPaperJam(ByVal device As Device)
        ' disable device UI
        device.ShowUI = False
        ' disable device when images are acquired
        device.DisableAfterAcquire = True
                
        ' open the device
        device.Open()
                
        ' set device settings
        device.PixelType = PixelType.RGB
        device.UnitOfMeasure = UnitOfMeasure.Inches
        device.Resolution = New Resolution(300.0F, 300.0F)
                
        Try
            ' get events supported by device
            Dim supportedDeviceEvents As DeviceEventId() = device.GetSupportedAsyncEvents()
            ' for each supported event
            For i As Integer = 0 To supportedDeviceEvents.Length - 1
                ' if device can report when paper is jammed
                If supportedDeviceEvents(i) = DeviceEventId.PaperJam Then
                    ' specify that device must report when paper is jammed
                    device.AsyncEvents = New DeviceEventId() {DeviceEventId.PaperJam}
                
                    ' subscribe to the device event
                    AddHandler device.AsyncEvent, New EventHandler(Of DeviceAsyncEventArgs)(AddressOf device_DeviceEvent)
                
                    Exit For
                End If
            Next
        Catch ex As Exception
            Console.WriteLine(ex.ToString())
        End Try
                
        ' subscribe to the Device.ImageAcquired, Device.ScanCompleted, ... events
        '...
                
        ' acquire images from device
        device.Acquire()
    End Sub
                
    ''' <summary>
    ''' Occurred the device event.
    ''' </summary>
    Private Sub device_DeviceEvent(ByVal sender As Object, ByVal e As DeviceAsyncEventArgs)
        Console.WriteLine("Paper is jammed.")
    End Sub
    /// <summary>
    /// Detects the paper jamm.
    /// </summary>
    public void DetectPaperJam(Device device)
    {
        // disable device UI
        device.ShowUI = false;
        // disable device when images are acquired
        device.DisableAfterAcquire = true;
                
        // open the device
        device.Open();
                
        // set device settings
        device.PixelType = PixelType.RGB;
        device.UnitOfMeasure = UnitOfMeasure.Inches;
        device.Resolution = new Resolution(300f, 300f);
                
        try
        {
            // get events supported by device
            DeviceEventId[] supportedDeviceEvents = device.GetSupportedAsyncEvents();
            // for each supported event
            for (int i = 0; i < supportedDeviceEvents.Length; i++)
            {
                // if device can report when paper is jammed
                if (supportedDeviceEvents[i] == DeviceEventId.PaperJam)
                {
                    // specify that device must report when paper is jammed
                    device.AsyncEvents = new DeviceEventId[] { DeviceEventId.PaperJam };
                
                    // subscribe to the device event
                    device.AsyncEvent += new EventHandler<DeviceAsyncEventArgs>(device_DeviceEvent);
                
                    break;
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
                
        // subscribe to the Device.ImageAcquired, Device.ScanCompleted, ... events
        //...
                
        // acquire images from device
        device.Acquire();
    }
                
    /// <summary>
    /// Occurred the device event.
    /// </summary>
    private void device_DeviceEvent(object sender, DeviceAsyncEventArgs e)
    {
        Console.WriteLine("Paper is jammed.");
    }
    Requirements

    Target Platforms: Windows 8, Windows 7, Windows Vista, Windows XP, Windows Server 2012, Windows Server 2008, Windows Server 2003

    See Also