Custom Conditional validation on strongly typed view in MVC

Question

I have a Person model and a student model. The student model has 2 FKs of PersonIDs; one for student and the other for parent.

My view looks like this:

  @Html.EditorFor(m => m.student.Person.FirstName)
  @Html.EditorFor(m => m.student.Person.DOB)

  @Html.EditorFor(m => m.student.Father.FirstName)

The models would look like this:

  public partial class Person
  {
    public int PersonID { get; set; }

    [Required]
    [PlaceHolder("First Name")]
    public string FirstName { get; set; }

    [PlaceHolder("Birth Date")]
    public Nullable<System.DateTime> DOB { get; set; }
  }


 public partial class Student
 {
    public int Student_PersonID { get; set; }
    public int Parent_PersonID { get; set; }
 }

I want the DOB to be required field for the student but not for the parent. If I add [Required] attribute to the DOB element, then it requires it for both. Is there a way I can set a require a field on the view? or is there a way in the model or using validation attribute to do this?

fyi... i am using EF database first approach

thanks

score 2 · Answer 1 · edited May 23 '17 at 11:47

I would suggest having the view model match the fields that are displayed in the view. If later a field is to be removed from the view, then it will also be removed from the domain model.

In this case, if your view is to display the following fields:

StudentFirstName
StudentDOB
ParentFirstName
ParentDOB

Then I would suggest having the following view:

public class PersonViewModel
{
   public int StudentPersonID { get; set; }

   [Required]
   public string StudentFirstName { get; set; }

   [Required]
   public DateTime StudentDOB { get; set; }

   public int ParentPersonID { get; set; }

   [Required]
   public string ParentFirstName { get; set; }

   public DateTime ParentDOB { get; set; }
}

Or if instead you have 2 seperate views displaying:

StudentFirstName
StudentDOB

AND displaying:

ParentFirstName
ParentDOB

Then I would suggest having 2 seperate view models:

public class StudentViewModel
{
   public int StudentPersonID { get; set; }

   [Required]
   public string StudentFirstName { get; set; }

   [Required]
   public DateTime StudentDOB { get; set; }
}

public class ParentViewModel
{
   public int ParentPersonID { get; set; }

   [Required]
   public string ParentFirstName { get; set; }

   public DateTime ParentDOB { get; set; }
}

Using the view models in this way will allow you to use the [Required] data annotations for the fields that require them rather than trying to create a workaround. Note that the view models are not to be confused with the domain models and therefore this data would then need to be mapped to the domain model.

Hope this helps.

If your application is a simple application you may not need to create a seperate business logic layer and most books only present MVC with simple models which may be fine. However, if you search around you will find other examples where developers recommend having a view model seperate from a business model such as this

I would also recommend reading Wrox Professional Enterprise .Net 2009 where chapters 7 & 8 give great examples of the business layer with discussions of the Transaction Script pattern, Active Record pattern and Domain Model pattern.

do you know of any good tutorials/blogs that explains using the view model - domain model scenario? thanks — Imran, Oct 14 '11 at 13:55
I have updated the end of my answer in response to your question. — Dangerous, Oct 14 '11 at 14:47

score 0 · Answer 2 · answered Oct 13 '11 at 17:31

One way is to make a PersonRequired class that inherits from Person. Add a metadata class to PersonRequired so you have PersonRequiredMetaData and in that specific that the inherited DOB field is required. You would need to manually copy the values between the Person and PersonRequired classes or use AutoMapper. I hope there is a better answer than this!

Another option is to use FluentValidation that would let you do the validation separate from the model (doesn't use data annotations). I wonder if some people are using data annotations for database requirements and fluent validation for programmatic requirements.

Custom Conditional validation on strongly typed view in MVC

2 Answers2