Outlook.Inspector currWind = Globals.ThisAddIn.Application.ActiveInspector();
Outlook.AppointmentItem app = (Outlook.AppointmentItem)currWind.CurrentItem;
app.UserProperties.Add("testaddfiled", Outlook.OlUserPropertyType.olText, true, Type.Missing);
app.UserProperties["testaddfiled"].Value = "Green";
app.Subject = "测试自定义添加字段";
app.Save();
这样添加不成功