'宣言
Public Property MaxHeaderItems As System.Integer
public System.int MaxHeaderItems {get; set;}
解説
If no items are selected, the header displays the text specified by the Placeholder property.If the number of selected items is smaller than or equal to the value of the MaxHeaderItems property, the selected items are shown in the header. If the number of selected items is greater than MaxHeaderItems, the header displays the selected item count instead.