Exception handling in AX / Try catch throw in AX

public boolean createExcelApp()
{
boolean ret = true;
;
try
{
sysExcelApplication = SysExcelApplication::construct();
if (sysExcelApplication == null)
{
ret = false;
throw Exception::Error;
}
}
catch (Exception::Error)
{
error("@SYS59928");
}
return ret;
}

=============UPdate exception=========

System.Exception ex;

        try

        {

            tableBuffer.field = value;

            tableBuffer.update();

        }

        catch(ex)

        {

            System.String messageEx = ex.Message;

            errorMessage = messageEx;

        }