TwainException Class

C#
Visual Basic
Java
Objective-C
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

[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.

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

Copy Code

Imports Leadtools
Imports Leadtools.Twain

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 IntPtr)
   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

using Leadtools;
using Leadtools.Twain;

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

   e.Cancel = false;
}
public void TwainExceptionExample(IntPtr 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

Reference

TwainException Members
Leadtools.Twain Namespace