public IEnumerable <ValidationResult> Validate(ValidationContext validationContext)
{
IGradeService gradeService = DependencyResolver.Current.GetService <IGradeService>();
Grade grade = gradeService
.All()
.FirstOrDefault(
g => g.GradeYear == this.GradeYear &&
(g.AcademicYear.StartDate == this.AcademicYearStartDate ||
g.AcademicYear.EndDate == this.AcademicYearEndDate));
if (grade != null)
{
yield return(new ValidationResult(string.Format("Grade {0} already exists", this.GradeYear)));
}
if (this.AcademicYearEndDate < DateTime.Now)
{
yield return(new ValidationResult("Grades cannot be added to already completed academic years."));
}
}
