The control you are using looks like the System.Windows.Forms.MonthCalendar control, which is supplied by Microsoft as part of the .net framework, so any questions about it really ought to be directed to Microsoft. I've tried it using both SharpDevelop 5.2 and Visual Studio 2015 community edition, and in neither can I select more than 7 days, so this is a restriction imposed by the control rather than by the IDE.
I can answer your second question (albeit in C#, sorry). If your MonthCalendar instance is called monthCalendar1 then this should do the trick:
public Collection<DateTime> SelectedDays
{
get
{
SelectionRange range = monthCalendar1.SelectionRange;
Collection<DateTime> returnValue = new Collection<DateTime>();
for (DateTime d = range.Start; d <= range.End; d = d.AddDays(1))
{
returnValue.Add(d);
}
return returnValue;
}
}
Hope this helps.
Simon