The SelectedActivities of the xamOutlookCalendarView is synchronized with the SelectedActivities of the ScheduleControlBase within for the current view (i.e. the DayView, MonthView or ScheduleView). I verified that clearing the collection or removing an item does affect the display. Adding an item to the selection is a bit more complicated because you have to get the Activity from the XamScheduleDataManager which depending on the DataConnector you are using (and its underlying storage) could be synchronous or asynchronous. Here's a simplified example. Note there is currently no public method for bringing an activity into view so you may want to submit a suggestion for adding that.

  private void OnSearchClick(object sender, RoutedEventArgs e)
  {
   string text = this.searchText.Text;
   var data = (ScheduleData)this.DataContext;
   var dataManager = this.view.DataManager;
   var tzProvider = dataManager.DataConnector.TimeZoneInfoProviderResolved;

   if (string.IsNullOrEmpty(text))
    return;
   // this is just a simple search to find the first. you'd probably want to 
   // make you're own routine that continues/starts from the selected activity
   // and then wraps around as needed or possibly that just searches within a 
   // given range
   foreach (var dataItem in data.Appointments)
   {
    string subject = dataItem.Subject;
    if (subject != null && subject.IndexOf(text, StringComparison.CurrentCultureIgnoreCase) >= 0)
    {
     Resource resource = dataManager.ResourceItems.GetResourceFromId(dataItem.OwningResourceId);
     ResourceCalendar calendar = resource.Calendars.FirstOrDefault((c) => c.Id == dataItem.OwningCalendarId);
     Debug.Assert(calendar != null);
     if (calendar != null)
     {
      ActivityQuery query = new ActivityQuery(ActivityTypes.Appointment, new DateRange(dataItem.Start, dataItem.End), calendar);
      var result = dataManager.GetActivities(query);
      if (result.IsComplete)
      {
       var activity = result.Activities.FirstOrDefault((a) => a.DataItem == dataItem);
       if (activity != null)
       {
        this.view.SelectedActivities.Clear();
        this.view.SelectedActivities.Add(activity);
        // currently there is no public method for bring an activity into view
        // but editing an activity will bring it into view. we can just 
        // temporarily prevent editing
        if (dataManager.Settings == null)
         dataManager.Settings = new ScheduleSettings();
        if (dataManager.Settings.AppointmentSettings == null)
         dataManager.Settings.AppointmentSettings = new AppointmentSettings();
        var apptSettings = dataManager.Settings.AppointmentSettings;
        var cmd = new ScheduleControlBaseCommand(ScheduleControlCommand.EditSelectedActivity);
        var oldValue = apptSettings.AllowEdit;
        apptSettings.AllowEdit = false;
        cmd.Execute(this.view);
        apptSettings.AllowEdit = oldValue;
       }
      }
      else
      {
       // otherwise you have to hold the result, listen to the property change 
       // for when the IsComplete is true and then access the activies and 
       // manipulate the selected activities
       Debug.Assert(false, "Need to handle this");
      }
      break;
     }
    }
   }
  }