How to: Catch Exceptions

  • Article

During the synchronization process, both expected and unexpected exceptions can occur. You can determine which exceptions are non-critical and can be safely ignored and which exceptions are critical and should stop the synchronization process. Use the Exception class in a Try/Catch block to handle unexpected exceptions in your extensions. For more information about the Try/Catch block, see How to: Use the Try/Catch Block to Catch Exceptions on MSDN Web site.

Note

Catch only exceptions that you intend to handle. If you are going to throw another exception as part of your exception handler, either throw an UnexpectedDataException exception and include a string message argument to help identify the cause of the exception or re-throw the exception by using the Throw statement without any parameters. This preserves the stack trace.

The following example shows how to catch both expected and unexpected rules exceptions, log an exception, and determine how these exceptions should be handled.

Note

To use the following example, you must include a reference to the Microsoft.MetadirectoryServices.Logging assembly (logging.dll) in your project. For further information about logging messages, see Logging Extension Messages.

Public Sub Provision(ByVal mventry As MVEntry) _
    Implements IMVSynchronization.Provision

    Dim dn As ReferenceValue
    Dim container As String
    Dim rdn As String
    Dim csentry As CSEntry

    Try

        ' Determine the container and relative distinguished name
        ' of the new connector space entry.
        container = "OU=somecontainer,DC=fabrikam,DC=com"
        rdn = "CN=" & mventry("cn").Value
        dn = mventry.ConnectedMAs("Fabrikam AD MA").EscapeDNComponent(rdn).Concat(container)
        csentry = mventry.ConnectedMAs("Fabrikam AD MA").Connectors.StartNewConnector("user")
        csentry.DN = dn
        csentry.CommitNewConnector()

    Catch ex As ObjectAlreadyExistsException

        ' Ignore if the object already exists; join rules will join the existing object later.

    Catch ex As NoSuchAttributeException

        ' Ignore if the attribute on the mventry object is not available at this time.

    Catch ex As Exception

        ' Log exception, with timestamp, at level 1.
        Logging.Logging.Log("Caught exception " & ex.Message, True, 1)
        ' All other exceptions re-throw to rollback the object synchronization transaction and 
        ' report the error to the run history.
        Throw

    End Try

End Sub

void IMVSynchronization.Provision (MVEntry mventry)
{
    ReferenceValue dn;
    String container;
    String rdn;
    CSEntry csentry;    

    try
    {

      // Determine the container and relative distinguished name
      // of the new connector space entry.
      container = "OU=somecontainer,DC=fabrikam,DC=com";
      rdn = "CN=" + mventry["cn"].Value;
      dn = mventry.ConnectedMAs["Fabrikam AD MA"].EscapeDNComponent(rdn).Concat(container);
      csentry = mventry.ConnectedMAs["Fabrikam AD MA"].Connectors.StartNewConnector("user");
      csentry.DN = dn;
      csentry.CommitNewConnector();
    }

    catch(ObjectAlreadyExistsException)
    {

      // Ignore if the object already exists; join rules will join the existing object later.
    }

   catch(NoSuchAttributeException)
    {

      // Ignore if the attribute on the mventry object is not available at this time
   }

    catch(Exception ex)
    {

      // Log exception, with timestamp, at level 1.
      Logging.Logging.Log("Caught exception " + ex.Message, true, 1);

      // All other exceptions re-throw to rollback the object synchronization transaction and 
      // report the error to the run history.
      throw;
    }
}

See Also

Concepts

How to: Handle Exceptions
How to: Check for Necessary Attributes
Testing and Debugging Rules Extensions