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Welcome to Xceed Data Manipulation Components for .NET and .NET Standard / Basic Concepts / Exceptions

In This Topic
    Exceptions
    In This Topic

    An exception is any error condition or unexpected behavior encountered by an executing program. Whenever an error occurs, an object that derives from the System.Exception class is created to represent the exception.

    Before contacting support

    Whenever you contact technical support regarding an exception, please include the exception's type, message, stack trace and all InnerException objects. This information will allow for a quick diagnostis of the issue. Here is sample code that collects the required information:

    C#
    Copy Code 
    try
{
  /* ...Code that triggers an exception... */
}
catch( Exception exception )
{
  // Output some information about the exception
  System.Diagnostics.Debug.WriteLine( "-->{0}: {1}\n{2}", exception.GetType().Name, exception.Message, exception.StackTrace );

  // Fetch the inner exception
  exception = exception.InnerException;

  // While there is an exception
  while( exception != null )
  {
    // Output some information about it
    System.Diagnostics.Debug.WriteLine( "-->Inner exception: {0}: {1}\n{2}", exception.GetType().Name, exception.Message, exception.StackTrace );

    // Fetch the inner exception
    exception = exception.InnerException;
  }
}
    VB.NET
    Copy Code 
    Try
  ' ...Code that triggers an exception...
Catch exception As Exception
  ' Output some information about the exception
  System.Diagnostics.Debug.WriteLine("-->{0}: {1}" & Constants.vbLf & "{2}", exception.GetType().Name, exception.Message, exception.StackTrace)

  ' Fetch the inner exception
  exception = exception.InnerException

  ' While there is an exception
  Do While exception IsNot Nothing
        ' Output some information about it
        System.Diagnostics.Debug.WriteLine("-->Inner exception: {0}: {1}" & Constants.vbLf & "{2}", exception.GetType().Name, exception.Message, exception.StackTrace)

        ' Fetch the inner exception
        exception = exception.InnerException
  Loop

  ' OPTIONAL: Depending on the architecture of the application, it might be a good idea to rethrow the exception
  'Throw
End Try

    Handling exceptions

    The exceptions that can be thrown by Xceed Zip for .NET are handled in the same manner as regular run-time exceptions using Try/Catch blocks. It is possible to intercept the exceptions before they are thrown using the ItemException event in order to try and recover from the exception before it is actually thrown.

    The following table provides a listing of all the custom exceptions that can be thrown when an error occurs:

    Exception Description
    FileSystemException Exception that is thrown when an error occurs in the Xceed.FileSystem namespace.
    FileSystemInternalException Exception that is thrown when something unexpected occurs in the Xceed.FileSystem namespace.
    FileSystemIOException Exception that is thrown when an IO error occurs while reading from or writing to an AbstractFile object.
    ItemAlreadyExistsException Exception that is thrown when performing an operation on a FileSystemItem object that already exists.
    ItemDoesNotExistException Exception that is thrown when performing an operation on a FileSystemItem object that does not yet exist.
    ItemIsReadOnlyException Exception that is thrown when performing an operation on a FileSystemItem object that is read only.
    ItemIsRootFolderException Exception that is thrown when performing an operation on a FileSystemItem object that is a root folder that does not permit that operation.
    InvalidDecryptionPasswordException Exception that is thrown when the data could not be decrypted with the supplied decryption password.
    InvalidZipStructureException Exception that is thrown when the internal structure of a ZIP file is invalid.
    InvalidSfxModuleException Exception that is thrown when an invalid SFX binary is provided.
    ZipException Exception that is thrown when an error occurs in the Xceed.Zip namespace.
    ZipIOException Exception that is thrown when an IO exception occurs while reading from or writing to the ZIP file.
    QuickZipException Exception that is thrown when an error occurs in a method of the QuickZip class
    InvalidTarStructureException Exception that is thrown when the internal structure of a tar file is invalid. This exception is not available in Xceed's .NET Compact Framework products.
    InvalidGZipStructureException Exception that is thrown when the internal structure of a gzip file is invalid. This exception is not available in Xceed's .NET Compact Framework products.
    CompressionException Exception that is thrown when there is a problem compressing or decompressing data.
    CompressionInternalException Exception that is thrown when something unexpected occurs while compressing or decompressing data.

    The ZipException class derives directly from the FileSystemException class. All of the other exception classes defined within the Xceed.Zip namespace derive from the ZipException class.

    Demonstration

    The following example demonstrates how to use a Try/Catch statement when calling the Delete method on a ZippedFile that is contained within a corrupted zip file:

    C#
    Copy Code 
    try
{
  // Get a zip file on disk
  AbstractFile zipFile = new DiskFile( @"C:\Test.zip" );
  
  // Get a file located inside the zip archive
  AbstractFile zippedFile = new ZippedFile( zipFile, @"\file.txt" );
  
  zippedFile.Delete();
}
// Catch a specific exception type
catch( ItemDoesNotExistException )
{
  // We choose to ignore this error for this specific operation
}
// Catch all other exception types
catch( Exception exception )
{
  // Output some information about it
  System.Diagnostics.Debug.WriteLine( "-->{0}: {1}\n{2}", exception.GetType().Name, exception.Message, exception.StackTrace );

  // Fetch the inner exception
  exception = exception.InnerException;

  // While there is an exception
  while( exception != null )
  {
    // Output some information about it
    System.Diagnostics.Debug.WriteLine( "-->Inner exception: {0}: {1}\n{2}", exception.GetType().Name, exception.Message, exception.StackTrace );

    // Fetch the inner exception
    exception = exception.InnerException;
  }
  
  // OPTIONAL: Depending on the architecture of the application, it might be a good idea to rethrow the exception
  //throw;
}
    VB.NET
    Copy Code 
    Try
  ' Get a zip file on disk
  Dim zipFile As AbstractFile = New DiskFile("C:\Test.zip")

  ' Get a file located inside the zip archive
  Dim zippedFile As AbstractFile = New ZippedFile(zipFile, "\file.txt")

  zippedFile.Delete()
' Catch a specific exception type
Catch e1 As ItemDoesNotExistException
  ' We choose to ignore this error for this specific operation
' Catch all other exception types
Catch exception As Exception
  ' Output some information about it
  System.Diagnostics.Debug.WriteLine("-->{0}: {1}" & Constants.vbLf & "{2}", exception.GetType().Name, exception.Message, exception.StackTrace)

  ' Fetch the inner exception
  exception = exception.InnerException

  ' While there is an exception
  Do While exception IsNot Nothing
        ' Output some information about it
        System.Diagnostics.Debug.WriteLine("-->Inner exception: {0}: {1}" & Constants.vbLf & "{2}", exception.GetType().Name, exception.Message, exception.StackTrace)

        ' Fetch the inner exception
        exception = exception.InnerException
  Loop

  ' OPTIONAL: Depending on the architecture of the application, it might be a good idea to rethrow the exception
  'Throw
End Try

    Things you should consider

    The main questions you should ask yourself when handling exceptions are:

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