Question

I’m building a .Net 4.0 application for remote control of a scanner device. I have tried both TWAIN and WIA libraries, but I have the same problem. Scanning images without scanner selection and scanning settings dialogs.

I found a useful article on WIA scripting in .Net, and modified it to this:

private Image Scan(string deviceName)
{
    WiaClass wiaManager = null;       // WIA manager COM object
    CollectionClass wiaDevs = null;   // WIA devices collection COM object
    ItemClass wiaRoot = null;         // WIA root device COM object
    CollectionClass wiaPics = null;   // WIA collection COM object
    ItemClass wiaItem = null;         // WIA image COM object

    try
    {
        // create COM instance of WIA manager
        wiaManager = new WiaClass();

        // call Wia.Devices to get all devices
        wiaDevs = wiaManager.Devices as CollectionClass;
        if ((wiaDevs == null) || (wiaDevs.Count == 0))
        {
            throw new Exception("No WIA devices found!");
        }

        object device = null;
        foreach (IWiaDeviceInfo currentDevice in wiaManager.Devices)
        {
            if (currentDevice.Name == deviceName)
            {
                device = currentDevice;
                break;
            }
        }

        if (device == null)
        {
            throw new Exception
            (
                "Device with name \"" + 
                deviceName + 
                "\" could not be found."
            );
        }

        // select device
        wiaRoot = (ItemClass)wiaManager.Create(ref device); 

        // something went wrong
        if (wiaRoot == null)
        {
            throw new Exception
            (
                "Could not initialize device \"" + 
                deviceName + "\"."
            );
        }

        wiaPics = wiaRoot.GetItemsFromUI
        (
            WiaFlag.SingleImage,
            WiaIntent.ImageTypeColor
        ) as CollectionClass;

        if (wiaPics == null || wiaPics.Count == 0)
        {
            throw new Exception("Could not scan image.");
        }

        Image image = null;

        // enumerate all the pictures the user selected
        foreach (object wiaObj in wiaPics)
        {
            if (image == null)
            {
                wiaItem = (ItemClass)Marshal.CreateWrapperOfType
                (
                    wiaObj, typeof(ItemClass)
                );

                // create temporary file for image
                string tempFile = Path.GetTempFileName();

                // transfer picture to our temporary file
                wiaItem.Transfer(tempFile, false);

                // create Image instance from file
                image = Image.FromFile(tempFile);
            }

            // release enumerated COM object
            Marshal.ReleaseComObject(wiaObj);
        }

        if (image == null)
        {
            throw new Exception("Error reading scanned image.");
        }

        return image;
    }
    finally
    {
        // release WIA image COM object
        if (wiaItem != null)
            Marshal.ReleaseComObject(wiaItem);

        // release WIA collection COM object
        if (wiaPics != null)
            Marshal.ReleaseComObject(wiaPics);

        // release WIA root device COM object
        if (wiaRoot != null)
            Marshal.ReleaseComObject(wiaRoot);

        // release WIA devices collection COM object
        if (wiaDevs != null)
            Marshal.ReleaseComObject(wiaDevs);

        // release WIA manager COM object
        if (wiaManager != null)
            Marshal.ReleaseComObject(wiaManager);
    }
}

With this I actually managed to select the device from configuration (input parameter of the Scan method) and retrieve the resulting image after scan.

But the problem with scanning options dialog (Scan using DEVICENAME). As this is a remote control application, dialog will not be visible to the user, so I need to either skip it using default settings, or use settings from a configuration if necessary.

Scanning options dialog:

Answer 1

In the end I did not use the code written in the question for scanning dialogs. I found a useful example of Scanning with Windows Image Acquisition 2.0 which by the way also had a blocking dialog, but this was easily modified and in moments I had a simple class with a Scan(string scannerId) function which would just scan with a selected device and nothing more, see code () below:

using System;
using System.Collections.Generic;
using System.IO;
using System.Drawing;

namespace WIATest
{
    class WIAScanner
    {
        const string wiaFormatBMP = "{B96B3CAB-0728-11D3-9D7B-0000F81EF32E}";

        class WIA_DPS_DOCUMENT_HANDLING_SELECT
        {
            public const uint FEEDER = 0x00000001;
            public const uint FLATBED = 0x00000002;
        }

        class WIA_DPS_DOCUMENT_HANDLING_STATUS
        {
            public const uint FEED_READY = 0x00000001;
        }

        class WIA_PROPERTIES
        {
            public const uint WIA_RESERVED_FOR_NEW_PROPS = 1024;
            public const uint WIA_DIP_FIRST = 2;
            public const uint WIA_DPA_FIRST = WIA_DIP_FIRST + WIA_RESERVED_FOR_NEW_PROPS;
            public const uint WIA_DPC_FIRST = WIA_DPA_FIRST + WIA_RESERVED_FOR_NEW_PROPS;
            //
            // Scanner only device properties (DPS)
            //
            public const uint WIA_DPS_FIRST = WIA_DPC_FIRST + WIA_RESERVED_FOR_NEW_PROPS;
            public const uint WIA_DPS_DOCUMENT_HANDLING_STATUS = WIA_DPS_FIRST + 13;
            public const uint WIA_DPS_DOCUMENT_HANDLING_SELECT = WIA_DPS_FIRST + 14;
        }

        /// <summary>
        /// Use scanner to scan an image (with user selecting the scanner from a dialog).
        /// </summary>
        /// <returns>Scanned images.</returns>
        public static List<Image> Scan()
        {
            WIA.ICommonDialog dialog = new WIA.CommonDialog();
            WIA.Device device = dialog.ShowSelectDevice(WIA.WiaDeviceType.UnspecifiedDeviceType, true, false);

            if (device != null)
            {
                return Scan(device.DeviceID);
            }
            else
            {
                throw new Exception("You must select a device for scanning.");
            }
        }

        /// <summary>
        /// Use scanner to scan an image (scanner is selected by its unique id).
        /// </summary>
        /// <param name="scannerName"></param>
        /// <returns>Scanned images.</returns>
        public static List<Image> Scan(string scannerId)
        {
            List<Image> images = new List<Image>();

            bool hasMorePages = true;
            while (hasMorePages)
            {
                // select the correct scanner using the provided scannerId parameter
                WIA.DeviceManager manager = new WIA.DeviceManager();
                WIA.Device device = null;

                foreach (WIA.DeviceInfo info in manager.DeviceInfos)
                {
                    if (info.DeviceID == scannerId)
                    {
                        // connect to scanner
                        device = info.Connect();
                        break;
                    }
                }

                // device was not found
                if (device == null)
                {
                    // enumerate available devices
                    string availableDevices = "";
                    foreach (WIA.DeviceInfo info in manager.DeviceInfos)
                    {
                        availableDevices += info.DeviceID + "n";
                    }

                    // show error with available devices
                    throw new Exception("The device with provided ID could not be found. Available Devices:n" + availableDevices);
                }

                WIA.Item item = device.Items[1] as WIA.Item;

                try
                {
                    // scan image
                    WIA.ICommonDialog wiaCommonDialog = new WIA.CommonDialog();
                    WIA.ImageFile image = (WIA.ImageFile)wiaCommonDialog.ShowTransfer(item, wiaFormatBMP, false);

                    // save to temp file
                    string fileName = Path.GetTempFileName();
                    File.Delete(fileName);
                    image.SaveFile(fileName);
                    image = null;

                    // add file to output list
                    images.Add(Image.FromFile(fileName));
                }
                catch (Exception exc)
                {
                    throw exc;
                }
                finally
                {
                    item = null;

                    //determine if there are any more pages waiting
                    WIA.Property documentHandlingSelect = null;
                    WIA.Property documentHandlingStatus = null;

                    foreach (WIA.Property prop in device.Properties)
                    {
                        if (prop.PropertyID == WIA_PROPERTIES.WIA_DPS_DOCUMENT_HANDLING_SELECT)
                            documentHandlingSelect = prop;

                        if (prop.PropertyID == WIA_PROPERTIES.WIA_DPS_DOCUMENT_HANDLING_STATUS)
                            documentHandlingStatus = prop;
                    }

                    // assume there are no more pages
                    hasMorePages = false;

                    // may not exist on flatbed scanner but required for feeder
                    if (documentHandlingSelect != null)
                    {
                        // check for document feeder
                        if ((Convert.ToUInt32(documentHandlingSelect.get_Value()) &amp;amp;amp;amp; WIA_DPS_DOCUMENT_HANDLING_SELECT.FEEDER) != 0)
                        {
                            hasMorePages = ((Convert.ToUInt32(documentHandlingStatus.get_Value()) &amp;amp;amp;amp; WIA_DPS_DOCUMENT_HANDLING_STATUS.FEED_READY) != 0);
                        }
                    }
                }
            }

            return images;
        }

        /// <summary>
        /// Gets the list of available WIA devices.
        /// </summary>
        /// <returns></returns>
        public static List<string> GetDevices()
        {
            List<string> devices = new List<string>();
            WIA.DeviceManager manager = new WIA.DeviceManager();

            foreach (WIA.DeviceInfo info in manager.DeviceInfos)
            {
                devices.Add(info.DeviceID);
            }

            return devices;
        }

    }
}