Datepicker allows selecting below minimum date

Hi,
I have an issue with my datepicker. I set minimum date to today, but I can still select dates lower than my minimum date (though they appear to be with a darker font on the calendar), can I somehow restrict them?
Here is a part of my .cs:

mAvailableDate.Click += delegate {
mCurrentDate = Calendar.Instance;
int mYear = mCurrentDate.Get(CalendarField.Year);
int mMonth = mCurrentDate.Get(CalendarField.Month);
int mDay = mCurrentDate.Get(CalendarField.DayOfMonth);
DatePickerDialog mDate = new DatePickerDialog(this, this, mYear, mMonth, mDay);
var dp = mDate;
mDate.DatePicker.MinDate = (long)(DateTime.Now.Date - new DateTime(1970, 1, 1)).TotalMilliseconds;
mDate.Show();
};
Any help will be much appreciated.