DateTimePickerColumn.cs

public class DateTimePickerColumn : Panel
{
    // The type of the column: numbers or months
    public DateTimePickerColumnType Type { get; set; }
   
    // The number or month at the top of the column
    public int First { get; set; }
   
    // The selected number or month
    public int Selected { get; set; }
   
    public int Minimum {get; set; }
    public int Maximum {get; set; }
   
    public void ScrollUp()
    {
	--First; // Handle looping etc also
	UpdateItems();
    }
   
    public void ScrollDown()
    {
	++First; // Handle looping etc also
	UpdateItems();
    }
   
    protected override void MeasureOverride(Size size)
    {
        // ... Creates and measures enough ListBoxItems to fill size ...
		
        UpdateItems();
    }
   
    protected override ArrangeOverride(Size size)
    {
        // Arranges the ListBoxItems in a vertical stack
    }
	
    private void UpdateItems()
    {
        // Assigns a number or a month to each ListBoxItem, and sets IsSelected if
        // it's the currently selected item
    }
}

public enum DateTimePickerColumnType
{
	  Numeric,
	  Months,
}