ntwain/samples/WinForm32/Form1.cs

using NTwain;
using System;
using System.Diagnostics;
using System.Reflection;
using System.Windows.Forms;
using TWAINWorkingGroup;

namespace WinForm32
{
  public partial class Form1 : Form
  {
    private TwainSession twain;

    public Form1()
    {
      InitializeComponent();

      TwainPlatform.PreferLegacyDSM = true;

      twain = new TwainSession(Assembly.GetExecutingAssembly().Location);
      twain.StateChanged += Twain_StateChanged;
    }

    private static void Twain_StateChanged(TwainSession session, TWAINWorkingGroup.STATE state)
    {
      Console.WriteLine($"State changed to {state}");
    }

    protected override void OnHandleCreated(EventArgs e)
    {
      base.OnHandleCreated(e);


      var hwnd = this.Handle;
      var rc = twain.DGControl.Parent.OpenDSM(ref hwnd);
      Debug.WriteLine($"OpenDSM={rc}");

      if (rc == TWAINWorkingGroup.STS.SUCCESS)
      {
        Debug.WriteLine($"CloseDSM={rc}");
        rc = twain.DGControl.Parent.CloseDSM(ref hwnd);
      }
    }
  }
}