Attempt to resurrect my old triplet ideas with new data types and native methods.

samples/WinForm32/Form1.cs

@@ -0,0 +1,51 @@
+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();
+
+      InitTwain();
+    }
+
+    private void InitTwain()
+    {
+      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);
+      }
+    }
+  }
+}