There is no currently a property which can be used for this purpose, but you can achieve it easily by handling the Calendar.ItemSelectionChanged event. The following code gives an idea on how to do it:

private void calendar_ItemSelectionChanged(object sender, ItemSelectionEventArgs e)
{
	if (e.IsSelected)
	{
		calendar.ItemSelection.Clear();
		calendar.ItemSelection.Add(e.Item);
	}
} 

Meppy

Setting Selection.AllowMultiple to State.Disabled prevents users from selecting range of dates, i.e. they can only select a single date. Clicking and dragging with the mouse will not select several dates, but rather only the last pointed date before the mouse is released. For example, when this property is disabled, in a SingleMonth view the users would be able to select only a single day cell, while in Resource view, they would be able to select only a single moment in time (which usually results in the selection not being visible).

In general, Calendar.Selection corresponds to the date/time selection within the control, while Calendar.ItemSelection corresponds to the appointment selection.

Meppy