Nested view model doesn't validate from unit tests in .net with DataAnnotations

Question

I have an ApiController, in which I have a Post method that accepts a VariableTemplateViewModel, which looks like this:

public class VariableTemplateViewModel
{
    public VariableTemplateViewModel() { }

    public double Version { get; set; }

    [Required]
    public List<VariableViewModel> Variables { get; set; }
}

public class VariableViewModel
{
    public VariableViewModel() { }

    [Required(AllowEmptyStrings=false, ErrorMessage="Variable Name cannot be empty")]
    public string Name { get; set; }
}

Inside the Post method, I do a validation check, like so:

public void Post(long id, [FromBody]VariableTemplateViewModel model)
{
    if (!ModelState.IsValid )
    {
        throw new HttpResponseException(HttpStatusCode.BadRequest);
    }   
}

This works great and if I call it with a view model that has empty Name fields in the Variables list, it fails validation. However, when I try to validate this from the Unit Test, it only runs validations on VariableViewModel itself and not recursively the VariableViewModel. So, if I pass in null for the Variables, I get a validation error but if I pass in an empty string for Name, there are no validation errors.

[TestMethod]
public void Post_Returns_HttpResponseException_With_Empty_Variable_Name()
{
    var controller = new VariableController();
    var viewModel = new VariableTemplateViewModel
                    {
                        Version = 1,
                        Variables = new List<VariableViewModel> 
                        { 
                            new VariableViewModel { Name = "" }
                        }
                    };

    var validationContext = new ValidationContext(viewModel, null, null);

    var validationResults = new List<ValidationResult>();
    Validator.TryValidateObject(viewModel, validationContext, validationResults, true);
    foreach (var validationResult in validationResults)
    {
        controller.ModelState.AddModelError(validationResult.MemberNames.First(), validationResult.ErrorMessage);
    }

    // Assert

}

I have tried removing/adding empty constructors and initializing Variables inside the VariableTemplateViewModel constructor. I have even tried using Validator.TryValidateObject on viewModel.Variables directly to no avail.

Does anyone know how this can be fixed?

I ended up using github.com/reustmd/DataAnnotationsValidatorRecursive which does precisely what I was looking for. — reggaemahn
– reggaemahn, Commented Aug 24, 2016 at 7:17

Smit Patel · Accepted Answer · 2016-08-24 06:38:20Z

-1

I have a same problem and use this for the solution. May this help You.

public void Post(long id, [FromBody]VariableTemplateViewModel model)
{
    if (!ModelState.IsValid && TryValidateModel(model.NestedModel, "NestedModel."))
    {
        throw new HttpResponseException(HttpStatusCode.BadRequest);
    }   
}

Try this, Recursive Validation Using DataAnnotations

edited Aug 24, 2016 at 6:38

answered Aug 24, 2016 at 6:28

Smit Patel

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3 Comments

reggaemahn Over a year ago

Hey, thanks for the answer. However, in my case, the validation works fine in the Post method. It's the unit tests that are the problem. Since you can't invoke validation directly from unit tests by calling Post, I'm using Validator.TryValidateObject inside the TestMethod and that's where it's failing to validate the nested model.

Smit Patel Over a year ago

Try with the updated link, stackoverflow.com/questions/7663501/…

reggaemahn Over a year ago

I just tried that. Still doesn't work from the Test Method :(

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