c# - .NET MVC Custom Date Validator

Question

I'll be tackling writing a custom date validation class tomorrow for a meeting app i'm working on at work that will validate if a given start or end date is A) less than the current date, or B) the start date is greater than the end date of the meeting (or vice versa).

I think this is probably a fairly common requirement. Can anyone point me in the direction of a blog post that might help me out in tackling this problem?

I'm using .net 3.5 so i can't use the new model validator api built into .NET 4. THe project i'm working on is MVC 2.

UPDATE: THe class i'm writing needs to extend the System.ComponentModel.DataAnnotations namespace. In .NET 4 there is a IValidateObject interface that you can implement, that makes this sort of thing an absolute doddle, but sadly i can't use .Net 4. How do i go about doing the same thing in .Net 3.5?

Answer 1

public sealed class DateStartAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        DateTime dateStart = (DateTime)value;
        // Meeting must start in the future time.
        return (dateStart > DateTime.Now);
    }
}

public sealed class DateEndAttribute : ValidationAttribute
{
    public string DateStartProperty { get; set; }
    public override bool IsValid(object value)
    {
        // Get Value of the DateStart property
        string dateStartString = HttpContext.Current.Request[DateStartProperty];
        DateTime dateEnd = (DateTime)value;
        DateTime dateStart = DateTime.Parse(dateStartString);

        // Meeting start time must be before the end time
        return dateStart < dateEnd;
    }
}

and in your View Model:

[DateStart]
public DateTime StartDate{ get; set; }

[DateEnd(DateStartProperty="StartDate")]
public DateTime EndDate{ get; set; }

In your action, just check that ModelState.IsValid. That what you're after?