Data Annotations for validation, at least one required field?

Question

If I have a search object with a list of fields, can I, using the System.ComponentModel.DataAnnotations namespace, set it up to validate that at least one of the fields in t

Answer 1

This question is pretty old, but as of .NET 3.5 (I believe), IValidatableObject can help with tricky validation situations. You can implement it to validate arbitrary business rules. In this case, something like:

public IEnumerable Validate(ValidationContext validationContext)
{
    if (string.IsNullOrWhiteSpace(FieldOne) && string.IsNullOrWhiteSpace(FieldTwo))
        yield return new ValidationResult("Must provide value for either FieldOne or FieldTwo.", new string[] { "FieldOne", "FieldTwo" });
}