Start Visual Studio .NET.

Choose File->New->Project… from the menu.

In the New Project dialog box, choose either "Visual C# Projects" or "Visual Basic Projects" in the Projects Type List, and choose "Windows Application" in the Templates List.

Type the project name as "TwainDuplex" in the Project Name field, and then choose OK. If desired, type a new location for your project or select a directory using the Browse button, and then choose OK.

• Leadtools.dll
• Leadtools.Twain.dll
• Leadtools.Codecs.dll
• Leadtools.WinForms.dll

Go to the toolbox (View->Toolbox) and Drag and drop an instance of Button control to the top of the form and set the following properties for them:

Switch to Form1 code view (right-click Form1 in the solution explorer then select View Code ) and add the following lines at the beginning of the file:

            Imports Leadtools
            Imports Leadtools.Twain
            Imports Leadtools.Codecs
            Imports Leadtools.WinForms
            

            using Leadtools;
            using Leadtools.Twain;
            using Leadtools.Codecs;
            using Leadtools.WinForms;
            

Declare the following private variable:

            Private WithEvents twnSession As TwainSession
            

            private TwainSession twnSession;
            

Add an event handler to the Form1 Load event and code it as follows:

            Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
               Try
                  ' Unlock Document support.
                  ' Note that this is a sample key, which will not work in your toolkit.
                  Dim MY_LICENSE_FILE As String = "d:\temp\TestLic.lic"
                  Dim MY_DEVELOPER_KEY As String = "xyz123abc"
                  RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY)
                  twnSession = new TwainSession
                  twnSession.Startup(Me.Handle, "manufacturer", "productFamily", "version", "application", TwainStartupFlags.None)
               Catch ex As Exception
                  MessageBox.Show(ex.Message)
               End Try
            End Sub   
            

            private void Form1_Load(object sender, System.EventArgs e)
            {
               try
               {
                  // Unlock Document support.
                  // Note that this is a sample key, which will not work in your toolkit.
                  string MY_LICENSE_FILE = "d:\\temp\\TestLic.lic";
                  string MY_DEVELOPER_KEY = "xyz123abc";
                  RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY);
                  twnSession = new TwainSession();
                  twnSession.Startup(this.Handle, "manufacturer", "productFamily", "version", "application", TwainStartupFlags.None);
               }
               catch (Exception ex)
               {
                  MessageBox.Show(this, ex.Message);
               }
            }
            

Add an event handler to the Form1 Closing event and code it as follows:

            Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
               Try
                  twnSession.Shutdown()
               Catch ex As Exception
                  MessageBox.Show(ex.Message)
               End Try
            End Sub   
            

            private void Form1_FormClosing(object sender, FormClosingEventArgs e)
            {
               try
               {
                  twnSession.Shutdown();
               }
               catch (Exception ex)
               {
                  MessageBox.Show(this, ex.Message);
               }
            }
            

Add an event handler to the buttonAcquire Click event and code it as follows:

            Private Sub buttonAcquire_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttonAcquire.Click
               Dim twainCap As TwainCapability
               twnSession.SelectSource(String.Empty)
               Try
               twainCap = twnSession.GetCapability(TwainCapabilityType.Duplex, TwainGetCapabilityMode.GetValues)
                  If Not IsNothing(twainCap) Then
                     ' check if the selected driver supports duplex capability
                     If (twainCap.OneValueCapability.ItemType <> TwainItemType.Uint16) Then
                        twnSession.Shutdown()
                        Return
                     End If
                     Dim item As TwainCapabilityValue = CType(twainCap.OneValueCapability.Value, TwainCapabilityValue)
                     Select Case item
                        Case TwainCapabilityValue.DuplexNone
                           MessageBox.Show(Me, "Duplex capability is not supported in the selected driver")
                        Case TwainCapabilityValue.DuplexOnePassDuplex
                           MessageBox.Show(Me, "1 Pass Duplex capability is supported in the selected driver")
                        Case TwainCapabilityValue.DuplexTwoPassDuplex
                           MessageBox.Show(Me, "2 Pass Duplex capability is supported in the selected driver")
                     End Select
                     ' make sure the duplex capability is enabled
                     If item <> TwainCapabilityValue.DuplexNone Then
                        Dim enable As Boolean = True
                        twainCap.Information.Type = TwainCapabilityType.DuplexEnabled
                        twainCap.Information.ContainerType = TwainContainerType.OneValue
                        twainCap.OneValueCapability.ItemType = TwainItemType.Bool
                        twainCap.OneValueCapability.Value = CType(enable, Object)
                        twnSession.SetCapability(twainCap, TwainSetCapabilityMode.Set)
                        MessageBox.Show(Me, "The duplex capability is enabled")
                     End If
                  End If
               Catch ex As Exception
                  MessageBox.Show(Me, ex.Message)
               End Try
               ' try to acquire pages using duplex capability
               twnSession.Acquire(TwainUserInterfaceFlags.Show Or TwainUserInterfaceFlags.Modal)
            End Sub
            

            private void buttonAcquire_Click(object sender, System.EventArgs e)
            {
               TwainCapability twainCap;
               twnSession.SelectSource(string.Empty);
               try
               {
                  twainCap = twnSession.GetCapability(TwainCapabilityType.Duplex, TwainGetCapabilityMode.GetValues);
                  if (twainCap != null)
                  {
                     //  check if the selected driver supports duplex capability
                     if (twainCap.OneValueCapability.ItemType != TwainItemType.Uint16)
                     {
                        twnSession.Shutdown();
                        return;
                     }
                     TwainCapabilityValue item = (TwainCapabilityValue)twainCap.OneValueCapability.Value;
                     switch (item)
                     {
                        case TwainCapabilityValue.DuplexNone:
                           MessageBox.Show(this, "Duplex capability is not supported in the selected driver");
                           break;
                        case TwainCapabilityValue.DuplexOnePassDuplex:
                           MessageBox.Show(this, "1 Pass Duplex capability is supported in the selected driver");
                           break;
                        case TwainCapabilityValue.DuplexTwoPassDuplex:
                           MessageBox.Show(this, "2 Pass Duplex capability is supported in the selected driver");
                           break;
                     }
                     //  make sure the duplex capability is enabled
                     if (item != TwainCapabilityValue.DuplexNone)
                     {
                        bool enable = true;
                        twainCap.Information.Type = TwainCapabilityType.DuplexEnabled;
                        twainCap.Information.ContainerType = TwainContainerType.OneValue;
                        twainCap.OneValueCapability.ItemType = TwainItemType.Bool;
                        twainCap.OneValueCapability.Value = enable;
                        twnSession.SetCapability(twainCap, TwainSetCapabilityMode.Set);
                        MessageBox.Show(this, "The duplex capability is enabled");
                     }
                  }
               }
               catch (Exception ex)
               {
                  MessageBox.Show(this, ex.Message);
               }
               //  try to acquire pages using duplex capability
               twnSession.Acquire(TwainUserInterfaceFlags.Show | TwainUserInterfaceFlags.Modal);
            }
            

Build, and Run the program to test it.