Question

Here’s some sample code:

    private Outlook.Application applicationObject;
    public void OnConnection(object application, Extensibility.ext_ConnectMode connectMode, object addInInst, ref System.Array custom)
    {
        MessageBox.Show("on connection");
        applicationObject = (Outlook.Application)application;
        applicationObject.Explorers.NewExplorer += new Microsoft.Office.Interop.Outlook.ExplorersEvents_NewExplorerEventHandler(Explorers_NewExplorer);
    }

    void Explorers_NewExplorer(Microsoft.Office.Interop.Outlook.Explorer Explorer)
    {
        MessageBox.Show("new explorer");
    }

the “new explorer” message never appears on the screen because the NewExplorer event never fires, not even when I click on “Open in New Window”.

What could be wrong?

Answer 1

The Explorers instance on which you’re subscribing to the NewExplorer event is probably getting garbage-collected. To prevent this from happening, preserve a reference to it through an instance variable:

private Outlook.Application applicationObject;
private Outlook.Explorers explorers;

public void OnConnection(object application, Extensibility.ext_ConnectMode connectMode, object addInInst, ref System.Array custom)
{
    MessageBox.Show("on connection");
    applicationObject = (Outlook.Application)application;
    explorers = applicationObject.Explorers;
    explorers.NewExplorer += new Microsoft.Office.Interop.Outlook.ExplorersEvents_NewExplorerEventHandler(Explorers_NewExplorer);
}