TwainException Class

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

[SerializableAttribute()]
public class TwainException : Leadtools.LeadtoolsException, System.Runtime.InteropServices._Exception, System.Runtime.Serialization.ISerializable

'Declaration
 
<SerializableAttribute()>
Public Class TwainException 
   Inherits Leadtools.LeadtoolsException
   Implements System.Runtime.InteropServices._Exception, System.Runtime.Serialization.ISerializable

'Usage
 
Dim instance As TwainException

public sealed class TwainException : System.Runtime.InteropServices._Exception, ~Remove~

function Leadtools.Twain.TwainException()

[SerializableAttribute()]
public ref class TwainException : public Leadtools.LeadtoolsException, System.Runtime.InteropServices._Exception, System.Runtime.Serialization.ISerializable

The TwainException class defines a Code property that you can examine to determine what caused the error.

Default messages are implemented for each Code, you can however modify any message through the GetCodeMessage and SetCodeMessage methods.

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Public Sub _twainSession_AcquirePage(ByVal sender As Object, ByVal e As TwainAcquirePageEventArgs)
   Application.DoEvents()
   If Not e.Image Is Nothing Then
      e.Image.Dispose()
   End If

   e.Cancel = False
End Sub


Public Sub TwainExceptionExample(ByVal parent As IWin32Window)
   Dim session As TwainSession = Nothing

   Try
      ' initialize a new TWAIN session
      session = New TwainSession()
      session.Startup(parent, "manufacturer", "productFamily", "version", "application", TwainStartupFlags.None)
      AddHandler session.AcquirePage, AddressOf _twainSession_AcquirePage

      ' acquire a page, if paper jam, allow the user to retry
      Dim done As Boolean = False
      Do While Not done
         Try
            Dim res As DialogResult = session.Acquire(TwainUserInterfaceFlags.Modal Or TwainUserInterfaceFlags.Show)
            MessageBox.Show("Success")
            done = True
         Catch ex As TwainException
            If ex.Code = TwainExceptionCode.PaperJam Then
               If MessageBox.Show("Paper jam.  Fix and retry?", "TWAIN", MessageBoxButtons.YesNo) = DialogResult.No Then
                  done = True
               End If
            Else
               ' other error, propogate
               Throw ex
            End If
         End Try
      Loop
   Catch ex As TwainException
      MessageBox.Show(String.Format("Twain error:{0}Code: {1}{0}Message: {2}", Environment.NewLine, ex.Code, ex.Message))
   Catch ex As Exception
      MessageBox.Show(String.Format("Other error: Message:{0}", ex.Message))
   Finally
      If Not session Is Nothing Then
         session.Shutdown()
      End If
   End Try
End Sub

public void _twainSession_AcquirePage(object sender, TwainAcquirePageEventArgs e)
{
   Application.DoEvents();
   if(e.Image != null)
      e.Image.Dispose();

   e.Cancel = false;
}


public void TwainExceptionExample(IWin32Window parent)
{
   TwainSession session = null;

   try
   {
      // initialize a new TWAIN session
      session = new TwainSession();
      session.Startup(parent, "manufacturer", "productFamily", "version", "application", TwainStartupFlags.None);
      session.AcquirePage += new EventHandler<TwainAcquirePageEventArgs>(_twainSession_AcquirePage);

      // acquire a page, if paper jam, allow the user to retry
      bool done = false;
      while(!done)
      {
         try
         {
            DialogResult res = session.Acquire(TwainUserInterfaceFlags.Modal | TwainUserInterfaceFlags.Show);
            MessageBox.Show("Success");
            done = true;
         }
         catch(TwainException ex)
         {
            if(ex.Code == TwainExceptionCode.PaperJam)
            {
               if(MessageBox.Show("Paper jam.  Fix and retry?", "TWAIN", MessageBoxButtons.YesNo) == DialogResult.No)
                  done = true;
            }
            else
            {
               // other error, propogate
               throw ex;
            }
         }
      }
   }
   catch(TwainException ex)
   {
      MessageBox.Show(string.Format("Twain error:{0}Code: {1}{0}Message: {2}", Environment.NewLine, ex.Code, ex.Message));
   }
   catch(Exception ex)
   {
      MessageBox.Show(string.Format("Other error: Message:{0}", ex.Message));
   }
   finally
   {
      if(session != null)
         session.Shutdown();
   }
}

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

TwainException Members
Leadtools.Twain Namespace