Exception class hierarchy

The ABL exceptions classes are shown below, hierarchically. You can use the Object Browser or Class Browser in your .NET development environment to explore the hierarchy. The classes are part of the Progress.Open4GL.Exceptions namespace. 

System.Exception
  ApplicationException
    ProError
      Open4GLError   
  Progress.Open4GL.Exceptions
    ProException
      Open4GLException
         BusySessionException
         Progress.Open4GL.Exceptions.ConnectException
           AppServerIOException
           BadURLException
           BrokerIOException
           ConnectAIAException
           ConnectFailedException
           ConnectHttpAuthException
           ConnectHttpsAuthException
           ConnectProtocolException
           ConnectProxyAuthException
           HostUnknownException
           InvalidNameServerPortException
           MsgVersionInvalidException
           NameServerClientPortException
           NameServerClientPortRangeException
           NameServerClientPortRetryException
           NameServerCommunicationsException
           NameServerInterruptException
           NameServerMessageFormatException
           NoSuchAppServiceException
           SystemErrorException
           UnknowHostnameException
         OutputSetException
         Runtime4GLException
           RunTime4GLErrorException
             RunTime4GLAppErrorException
           RunTime4GLQuitException
           RunTime4GLStopException
             RunTime4GLLockConflictException
             RunTime4GLStopAfterException
             Runtime4GLStopErrorException
         MetaDataException
         SchemaValidationException
         SystemErrorException
       OutputSetException
  SystemException
    DataException
      ProDataException
        DeletedRowAccessException