Use the ID property to specify a specified even by its identifier. Use the ToString property to display information about fired event such us name, parameters, types and values. Use the CountParam property to count the parameters  of an OLE event. Use the Param property to get the event's parameter. Use the Value property to specify the value of the parameter. The following VB sample enumerates the arguments of an OLE event when ItemOLEEvent is fired.

Private Sub Tree1_ItemOleEvent(ByVal Item As EXTREELibCtl.HITEM, ByVal Ev As EXTREELibCtl.IOleEvent)
   Debug.Print "Event name:" & Ev.Name
   If (Ev.CountParam = 0) Then
      Debug.Print "The event has no arguments."
   Else
      Debug.Print "The event has the following arguments:"
      Dim i As Long
      For i = 0 To Ev.CountParam - 1
         Debug.Print Ev(i).Name; " = " & Ev(i).Value
      Next
   End If
End Sub

The following VC sample displays the events that an ActiveX control is firing while it is hosted by an item:

 #import <extree.dll> rename( "GetItems", "exGetItems" )

static CString V2S( VARIANT* pv, LPCTSTR szDefault = _T("") )
{
	if ( pv )
	{
		if ( pv->vt == VT_ERROR )
			return szDefault;

		COleVariant vt;
		vt.ChangeType( VT_BSTR, pv );
		return V_BSTR( &vt );
	}
	return szDefault;
}

void OnItemOleEventTree1(long Item, LPDISPATCH Ev) 
{
	EXTREELib::IOleEventPtr spEvent( Ev );
	CString strOutput;
	strOutput.Format( "Event's name: %s\n", spEvent->Name.operator const char *() );
	OutputDebugString( strOutput ); 
	if ( spEvent->CountParam == 0 )
		OutputDebugString( "The event has no parameters." ); 
	else
	{
		for ( long i = 0; i < spEvent->CountParam; i++ )
		{
			EXTREELib::IOleEventParamPtr spParam = spEvent->GetParam( COleVariant( i ) );
			strOutput.Format( "Name: %s, Value: %s\n", spParam->Name.operator const char *(), V2S( &spParam->Value ) );
			OutputDebugString( strOutput ); 
		}
	}
	OutputDebugString( "" ); 
}

The #import clause is required to get the wrapper classes for IOleEvent and IOleEventParam objects, that are not defined by the MFC class wizard. The same #import statement defines the EXTREELib namespace that include all objects and types of the control's TypeLibrary. In case your extree.dll library is located to another place than the system folder or well known path, the path to the library should be provided, in order to let the VC finds the type library.  

The following VB.NET sample displays the events that an ActiveX control is firing while it is hosted by an item:

Private Sub AxTree1_ItemOleEvent(ByVal sender As Object, ByVal e As AxEXTREELib._ITreeEvents_ItemOleEventEvent) Handles AxTree1.ItemOleEvent
    Debug.WriteLine("Event's name: " & e.ev.Name)
    Dim i As Long
    For i = 0 To e.ev.CountParam - 1
        Dim eP As EXTREELib.OleEventParam
        eP = e.ev(i)
        Debug.WriteLine("Name: " & e.ev.Name & " Value: " & eP.Value)
    Next
End Sub

The following C# sample displays the events that an ActiveX control is firing while it is hosted by an item:

private void axTree1_ItemOleEvent(object sender, AxEXTREELib._ITreeEvents_ItemOleEventEvent e)
{
	System.Diagnostics.Debug.WriteLine( "Event's name: " + e.ev.Name.ToString() );
	for ( int i= 0; i < e.ev.CountParam ; i++ )
	{
		EXTREELib.IOleEventParam evP = e.ev[i];
		System.Diagnostics.Debug.WriteLine( "Name: " + evP.Name.ToString() + ", Value: " + evP.Value.ToString() );
	}
}

The following VFP sample displays the events that an ActiveX control fires when it is hosted by an item:

*** ActiveX Control Event ***
LPARAMETERS item, ev

local s
s = "Event's name: " + ev.Name
for i = 0 to ev.CountParam - 1
		s = s +  "Name: " + ev.Param(i).Name + " ,Value: " + Str(ev.Param(i).Value)
endfor
wait window nowait s