DateGreaterThanAttribute

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

[AttributeUsage(AttributeTargets.Property)]
public class DateGreaterThanAttribute : ValidationAttribute
{
    public DateGreaterThanAttribute(string dateToCompareToFieldName)
    {
        DateToCompareToFieldName = dateToCompareToFieldName;
    }

    public string DateToCompareToFieldName { get; private set; }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value == null)
        {
            return ValidationResult.Success;
        }

        var laterDate = (DateTime?)value;
        var earlierDate = (DateTime?)validationContext
            .ObjectType
            .GetProperty(DateToCompareToFieldName)
            .GetValue(validationContext.ObjectInstance);

        if (laterDate > earlierDate)
        {
            return ValidationResult.Success;
        }

        return new ValidationResult("Date is not later than other.");
    }

    public override string FormatErrorMessage(string name)
    {
        return string.Format("{0} must be greather than {1}", name, this.DateToCompareToFieldName);
    }
}