Hooking up to an Item Changed Event in VSTO

After last night's mossig meeting and my Outlook/VSTO presentation someone asked me about the following scenario:
"I want to capture the fact that a user changes an email address in the Outlook contacts list and call into a custom Web Service to update my LOB-system recording that change." For those that have used the Outlook object model before that is probably not a difficult task, for those new to Outlook and tempted by VSTO to give Office Integration a go it may not be so obvious so I decided to write a little bit of demo-code in C# to show how to setup the event handler, I'll leave the actual call to a Web Service or updating a database using .net classes up to the student as an exercise ;-). Start by creating a new Outlook Addin project, open ThisAddIn.cs and add the code below.


.....
using Outlook = Microsoft.Office.Interop.Outlook;
using Office = Microsoft.Office.Core;
.....
public partial class ThisAddIn
{
Outlook.MAPIFolder contactfolder;
Outlook.Items items; // This on is important, keep the reference at the addin level, a local var in the startup method will get garbage collected and the events will stop firing.

private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
Outlook.NameSpace ns;
ns = this.Application.GetNamespace("MAPI");
contactfolder = ns.GetDefaultFolder
(Outlook.OlDefaultFolders.olFolderContacts);
items = contactfolder.Items;
items.ItemChange +=
new Outlook.ItemsEvents_ItemChangeEventHandler(ItemChanged);

}
private void ItemChanged( object item )
{
Outlook.ContactItem contact;
contact = (Outlook.ContactItem)item;
// This is were you do your thing......
System.Windows.Forms.MessageBox.Show(contact.Email1Address);
}
.....

The same is available for ItemAdd, for delete events you would have to hookup an ItemAdd to the DeletedItems folder.