Access Violation error

[saurabhabh]

This is the code that I have written

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Data;
using System.Windows.Media.Imaging;
using System.Windows.Threading;
using Saraff.Twain;
using Saraff.Twain.Aux;

namespace Inweon_Grain_Management_System.Services
{
    class TWAINScannerService
    {
        Bitmap scanImage = null;
        Saraff.Twain.Twain32 twain = null;
        public TWAINScannerService()
        {
            twain = new Saraff.Twain.Twain32();
            twain.ShowUI = false;
            twain.AppProductName = "Saraff.Twain";
            twain.IsTwain2Enable = true;
            twain.OpenDSM();
            twain.SetupFileXferEvent += new System.EventHandler<Saraff.Twain.Twain32.SetupFileXferEventArgs>(this._twain32_SetupFileXferEvent);
            twain.FileXferEvent += new System.EventHandler<Saraff.Twain.Twain32.FileXferEventArgs>(this._twain32_FileXferEvent);

            twain.AcquireError += new System.EventHandler<Saraff.Twain.Twain32.AcquireErrorEventArgs>(this._twain32_AcquireError);

        }
        public void Scan()
        {
            #region Set Capabilities

            twain.SourceIndex = 0;
            twain.OpenDataSource();

            try
            {
                twain.SetCap(TwCap.XResolution, 600);
            }
            catch
            {
            }

            try
            {
                twain.SetCap(TwCap.YResolution, 600);
            }
            catch
            {
            }

            try
            {
                twain.SetCap(TwCap.IPixelType, TwPixelType.RGB);
            }
            catch
            {
            }

            try
            {
                twain.SetCap(TwCap.IXferMech, TwSX.File);
            }
            catch
            {
            }

            try
            {
                twain.SetCap(TwCap.ImageFileFormat, TwFF.Bmp);
            }
            catch
            {
            }

            try
            {
                twain.Capabilities.Indicators.Set(false);
            }
            catch
            {
            }

            twain.Capabilities.XferCount.Set(1);

            #endregion

            twain.Acquire();

        }

        private void _twain32_AcquireError(object sender, Twain32.AcquireErrorEventArgs e)
        {
            throw e.Exception;
        }
        private void _twain32_SetupFileXferEvent(object sender, Twain32.SetupFileXferEventArgs e)
        {
            try
            {
                e.FileName = string.Format(@"FileXferTransfer_{0}.{1}", DateTime.Now.ToString("yyyyMMddHHmmss"), this.twain.Capabilities.ImageFileFormat.GetCurrent().ToString().ToLower());
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        private void _twain32_FileXferEvent(object sender, Twain32.FileXferEventArgs e)
        {
            try
            {
                this.scanImage = Image.FromFile(e.ImageFileXfer.FileName) as Bitmap;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
    }
}

Now When Acquire() is called it gives me below error with attached stack trace Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

at Saraff.Twain.Twain32._DsmEntry.DsInvoke[T](TwIdentity origin, TwIdentity dest, TwDG dg, TwDAT dat, TwMSG msg, T& data) at Saraff.Twain.Twain32._EnableDataSource() at Saraff.Twain.Twain32.Acquire() at Inweon_Grain_Management_System.Services.TWAINScannerService.Scan() in E:\Saurabh\Work\Inweon\inweon-grain-management-system\Inweon Grain Management System\Services\TWAINScannerService.cs:line 96 at Inweon_Grain_Management_System.Services.MockMeasurementService.LoadGrainReadings(GateKeeperService gateKeeperService) in E:\Saurabh\Work\Inweon\inweon-grain-management-system\Inweon Grain Management System\Services\MockMeasurementService.cs:line 23 at Inweon_Grain_Management_System.MainWindowUSA.Measure(GateKeeperService gateKeeperService) in E:\Saurabh\Work\Inweon\inweon-grain-management-system\Inweon Grain Management System\MainWindowUSA.xaml.cs:line 216 at Inweon_Grain_Management_System.MainWindowUSA.b__25_0() in E:\Saurabh\Work\Inweon\inweon-grain-management-system\Inweon Grain Management System\MainWindowUSA.xaml.cs:line 194 at System.Threading.Tasks.Task.Execute() at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot) at System.Threading.Tasks.Task.ExecuteEntry(Boolean bPreventDoubleExecution) at System.Threading.ThreadPoolWorkQueue.Dispatch()

Any help will be really great. I am running a x64 machine and have installed a virtual scanner. (Saraff.Twain.DS.Screen.Installer_x64)

[saraff-9EB1047A4BEB4cef8506B29BA325BD5A]

Hello, @saurabhabh I think that it related with the multithreading accessing. If you need to the async invocation that see the Saraff.Twain.NET Outproc Samples or the Saraff.Twain.NET Service Samples

[saurabhabh]

I followed one of the WPF examples (sample2) and it worked. Thanks for the quick response though.

[EugeneQilo]

@saraff-9EB1047A4BEB4cef8506B29BA325BD5A Is there another alternative solution for .NET Core? The Saraff.Twain.Aux has dependency on Saraff.Twain.NET