Progress with OpenDS.

samples/WinForm32/Form1.cs

@@ -24,7 +24,7 @@ namespace WinForm32
 
     private static void Twain_StateChanged(TwainSession session, STATE state)
     {
-      Console.WriteLine($"State changed to {state}");
+      Debug.WriteLine($"State changed to {state}");
     }
 
     protected override void OnHandleCreated(EventArgs e)
@@ -35,6 +35,7 @@ namespace WinForm32
       var hwnd = this.Handle;
       var rc = twain.DGControl.Parent.OpenDSM(ref hwnd);
       Debug.WriteLine($"OpenDSM={rc}");
+
     }
 
     protected override void OnClosing(CancelEventArgs e)

src/NTwain/Triplets/DATIdentity.cs

@@ -0,0 +1,96 @@
+using System;
+using TWAINWorkingGroup;
+
+namespace NTwain.Triplets
+{
+  /// <summary>
+  /// Contains calls used with <see cref="DG.CONTROL"/> and <see cref="DAT.IDENTITY"/>.
+  /// </summary>
+  public class DATIdentity : TripletBase
+  {
+    public DATIdentity(TwainSession session) : base(session)
+    {
+    }
+
+    /// <summary>
+    /// Loads and opens the specified DS.
+    /// </summary>
+    /// <param name="ds"></param>
+    /// <returns></returns>
+    public STS OpenDS(ref TW_IDENTITY_LEGACY ds)
+    {
+      STS rc;
+      if ((rc = DoIt(MSG.OPENDS, ref ds, true)) == STS.SUCCESS)
+      {
+        Session.State = STATE.S4;
+        //// determine memory mgmt routines used
+        //if ((((DG)Session._appIdentityLegacy.SupportedGroups) & DG.DSM2) == DG.DSM2)
+        //{
+        //  TW_ENTRYPOINT_DELEGATES entry = default;
+        //  if (Session.DGControl.EntryPoint.Get(ref entry) == STS.SUCCESS)
+        //  {
+        //    Session._entryPoint = entry;
+        //  }
+        //}
+      }
+      return rc;
+    }
+
+    ///// <summary>
+    ///// Closes the currently open DS.
+    ///// </summary>
+    ///// <returns></returns>
+    //public STS CloseDS(ref IntPtr hwnd)
+    //{
+    //  STS rc;
+    //  if ((rc = DoIt(MSG.CLOSEDSM, ref hwnd)) == STS.SUCCESS)
+    //  {
+    //    Session._hwnd = IntPtr.Zero;
+    //    Session._entryPoint = default;
+    //    Session.State = STATE.S2;
+    //  }
+    //  return rc;
+    //}
+
+
+    STS DoIt(MSG msg, ref TW_IDENTITY_LEGACY ds, bool updateSource)
+    {
+      var rc = STS.FAILURE;
+      if (TwainPlatform.IsWindows)
+      {
+        var app = Session._appIdentityLegacy;
+        if (TwainPlatform.Is32bit && TwainPlatform.PreferLegacyDSM)
+        {
+          rc = (STS)NativeMethods.WindowsTwain32DsmEntryIdentity(ref app, IntPtr.Zero, DG.CONTROL, DAT.IDENTITY, msg, ref ds);
+        }
+        else
+        {
+          rc = (STS)NativeMethods.WindowsTwaindsmDsmEntryIdentity(ref app, IntPtr.Zero, DG.CONTROL, DAT.IDENTITY, msg, ref ds);
+        }
+        if (updateSource && rc == STS.SUCCESS)
+        {
+          Session._dsIdentityLegacy = ds;
+        }
+      }
+      else if (TwainPlatform.IsMacOSX)
+      {
+        var app = Session._appIdentityOSX;
+        TW_IDENTITY_MACOSX osxds = ds;
+        if (TwainPlatform.PreferLegacyDSM)
+        {
+          rc = (STS)NativeMethods.MacosxTwainDsmEntryIdentity(ref app, IntPtr.Zero, DG.CONTROL, DAT.IDENTITY, msg, ref osxds);
+        }
+        else
+        {
+          rc = (STS)NativeMethods.MacosxTwaindsmDsmEntryIdentity(ref app, IntPtr.Zero, DG.CONTROL, DAT.IDENTITY, msg, ref osxds);
+        }
+        if (updateSource && rc == STS.SUCCESS)
+        {
+          Session._dsIdentityOSX = osxds;
+          Session._dsIdentityLegacy = osxds;
+        }
+      }
+      return rc;
+    }
+  }
+}

src/NTwain/Triplets/DGControl.cs

@@ -15,5 +15,8 @@
     private DATEntryPoint? _entryPoint;
     public DATEntryPoint EntryPoint => _entryPoint ??= new DATEntryPoint(Session);
 
+    private DATIdentity? _identity;
+    public DATIdentity Identity => _identity ??= new DATIdentity(Session);
+
   }
 }