public class <event_name>
{
        public bool OnEvent( Context in_context )
        {
                ...
        }
}

CStatus <event_name>_OnEvent( CRef& in_context )
{ 
        ... 
}

function <event_name>_OnEvent( in_context )
{ 
        ... 
}

def <event_name>_OnEvent( in_context ):
        ...

Function <event_name>_OnEvent( in_context )
        ...
End Function

sub <event_name>_OnEvent 
{ 
        my $in_context = shift; 
}

// C++ code generated by the Event Wizard
#include <xsi_application.h>
#include <xsi_context.h>
#include <xsi_pluginregistrar.h>
#include <xsi_status.h>
using namespace XSI; 

SICALLBACK XSILoadPlugin( PluginRegistrar& in_reg )
{
 in_reg.PutAuthor(L"sblair");
 in_reg.PutName(L"NewEvent Plug-in");
 in_reg.PutEmail(L"");
 in_reg.PutURL(L"");
 in_reg.PutVersion(1,0);
 in_reg.RegisterEvent(L"siOnSelectionChangeEvent",siOnSelectionChange);
 //RegistrationInsertionPoint - do not remove this line

 return CStatus::OK;
}

SICALLBACK XSIUnloadPlugin( const PluginRegistrar& in_reg )
{
 CString strPluginName = in_reg.GetName();
 Application().LogMessage(strPluginName + L" has been unloaded.");
 return CStatus::OK;
}

// Callback for the siOnSelectionChangeEvent event.

SICALLBACK siOnSelectionChangeEvent_OnEvent( CRef& in_ctxt )
{
 Context ctxt( in_ctxt );
 Application().LogMessage(L"siOnSelectionChangeEvent_OnEvent called");

 Application().LogMessage(L"ChangeType: " + CString(ctxt.GetAttribute(L"ChangeType")));

//  TODO: Put your code here.

//  Returns CStatus::False if you don't want to abort the event.
 return CStatus::False;
}