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Twain Duplex Tutorial
Take the following steps to start a project:
  1. Start Visual Studio .NET.
  2. Choose File->New->Project… from the menu.
  3. 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.
  4. Type the project name as "GetFastTwainScan" 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 .
  5. In the "Solution Explorer" window, right-click on the "References" folder, and select "Add Reference…" from the context menu. In the "Add Reference" dialog box, select the ".NET" tab and browse to Leadtools For .NET "\LEAD Technologies\LEADTOOLS 15\Bin\DotNet\Win32 " folder and select the following DLLs:
    • Leadtools.dll
    • Leadtools.Twain.dll
    • Leadtools.Codecs.dll
    • Leadtools.WinForms.dll
    Click the Select button and then press the OK button to add the above DLLs to the application.
  6. Go to the toolbox (View->Toolbox) and Drag and drop a 1 instance of Button control to the top of the form and set the following properties for them:
    TextName
  7. 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:

    [Visual Basic]

    
    Imports Leadtools
    Imports Leadtools.Twain
    Imports Leadtools.Codecs
    Imports Leadtools.WinForms
    
    [C#]
    
    using Leadtools;
    using Leadtools.Twain;
    using Leadtools.Codecs;
    using Leadtools.WinForms;
    
  8. Declare the following private variable:

    [Visual Basic]

    
    Private WithEvents twnSession As TwainSession
    
    [C#]
    
    private TwainSession twnSession;
    
  9. Add an event handler to the Form1 Load event and code it as follows:

    [Visual Basic]

    
    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.
          RasterSupport.Unlock(RasterSupportType.Document, "TestKey")
    
          twnSession = new TwainSession
          twnSession.Startup(Me, "LEAD Technologies, Inc.", "LEAD Twain .NET", "Version 14", "LEADTools Twain test sample", TwainStartupFlags.None)
       Catch ex As Exception
          MessageBox.Show(ex.Message)
       End Try
    End Sub   
    
    [C#]
    
    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.
          RasterSupport.Unlock(RasterSupportType.Document, "TestKey");
    
          twnSession = new TwainSession();
          twnSession.Startup(this, "LEAD Technologies, Inc.", "LEAD Twain .NET", "Version 14", "LEADTools Twain test sample", TwainStartupFlags.None);
       }
       catch (Exception ex)
       {
          MessageBox.Show(this, ex.Message);
       }
    }
    
  10. Add an event handler to the Form1 Closing event and code it as follows:

    [Visual Basic]

    
    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   
    
    [C#]
    
    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
       try
       {
          twnSession.Shutdown();
       }
       catch (Exception ex)
       {
          MessageBox.Show(this, ex.Message);
       }
    }
    
  11. Add an event handler to the buttonAcquire Click event and code it as follows:

    [Visual Basic]

    
    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
    
    [C#]
    
    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);
    }
    
  12. Build, and Run the program to test it.