在此Outlook2007应用程序中，为什么Explorers.NewExplorer事件没有触发？

Question

下面是一些示例代码：

    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");
    }

"new explorer“消息从来不会出现在屏幕上，因为NewExplorer事件从来不会触发，甚至当我点击”在新窗口中打开“时也不会。

会出什么问题呢？

Answer 1

订阅NewExplorer事件的Explorers实例可能会被垃圾回收。要防止这种情况发生，请通过实例变量保留对它的引用：

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);
}