Custom Validation Attribute for three levels deep model

Question

Hi I have a situation in witch I have to create some custom validation attributes because the way my model is created.The model looks something like this:

public class EvaluationFormDataContract
{
    public int StudentAssignmentInstanceId { get; set; }

    public int EvaluationType { get; set; }


    public List<CategoriesOnEvaluationDataContract> Categories { get; set; }
}

  public class CategoriesOnEvaluationDataContract
{
    public string Memo { get; set; }

    public int CategoryId { get; set; }

    public List<QuestionsOnEvalCategoryDataContract> Questions { get; set; }

    // Fields needed for validation
    public bool? HasMemo { get; set; }

    public bool MemoIsMandatory { get; set; }
}

    public class QuestionsOnEvalCategoryDataContract
{
    public string Memo { get; set; }

    public string Grade { get; set; }

    public int QuestionId { get; set; }

    // Fields needed for validation
    public bool HasGrade { get; set; }

    public bool HasMemo { get; set; }

    public bool ShowOnlyMemo { get; set; }
}

As it can be seem the model is composed two levels deep. And I will have to validate starting from the second level , where I will check if the model HasMemo and if MemoIsMandatory.

The third validation should be done at the 3rd level where I have to check if it HasGrade and HasMemo.

Normaly if it were up to me I would split this in three separate calls to the server but we are depending on an legacy project and for the moment I have to make this work.

The post action will be called via an ajax call and will have all this data into it.

Now my question is where should I add the validation attribute?

Should it be added at the top on Categories , making it directly responsible for all the levels of the model?

Or I should place it on each model and find a way to make the data binder aware of it? If so how can I do this?

Answer 1

You can do both. If you implement System.ComponentModel.DataAnnotations.IValidatableObject interface at the top-most level, you can do whatever you want with the properties in the entire graph and return the errors.

public class EvaluationFormDataContract : IValidatableObject
{
        // All properties go here

        public IEnumerable<ValidationResult> Validate(
                                 ValidationContext validationContext)
        {
            if (// do what you want)
                yield return new ValidationResult("message");
        }
}

Or, you can apply attributes at the lower levels and automatically binding takes care of validating the properties in the graph. You don't need to do anything special.