Applying Required Attribute Validation on a Collection, IEnumerable - asp.net-mvc

Question

How can I apply Required Attribute like validation to the following without knowing how many elements will be in each collection:
public class MyViewPageViewModel
{
[Required]
public List<int> IntCollection { get; set; }
[Required]
public Dictionary<int, string> IntAndStringAllValueCollection { get; set; }
[Required("Value")]
public Dictionary<int, string> IntAndStringValueValidationCollection { get; set; }
[Required("Name","HairColor")]
public List<Person> PersonNameValidationCollection { get; set; }
}
For IntCollection I want every element to be required. For IntAndStringAllValueCollection I want every Key and every Value to be required. For IntAndStringValueValidationCollection I do not want the Key to be required but I want the Value to be required.

Answer 1

Although I'd like to be able to do it as expressed above, one way to get around the problem is like so:
public class PageViewModel
{
public List<RequiredStartAndEndDateTuple> OnlineDates { get; set; }
}
public class RequiredStartAndEndDateTuple
{
public RequiredStartAndEndDateTuple() { }
public RequiredStartAndEndDateTuple(DateTime? startDate, DateTime? endDate)
{
OnlineStartDate = startDate;
OnlineEndDate = endDate;
}
[Required(ErrorMessage = "Start Date Required")]
public DateTime? OnlineStartDate { get; set; }
//-- Note, no attribute means end date not required
public DateTime? OnlineEndDate { get; set; }
}
And if you're interested in the Controller & View Bits, check out:
http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx
Specifically grab the project source code and check out the 'Sequential' page using the strongly typed helpers