Custom validation fires if in model class but not on page property - asp.net-core

Question

I have a contact Razor page implemented in ASP.NET Core 2.0. I am using model binding and custom validation.
If I use custom validation on a separate model class, the validation method is called. If I use custom validation on a property on the PageModel, the validation method is not called. However, all properties are successfully bound.
Here's the PageModel class and the separate model class:
public class ContactModel : PageModel
{
[BindProperty]
public ContactMessageModel ContactMessageModel { get; set; }
[BindProperty, CustomValidation]
public string SomeData { get; set; }
public IActionResult OnPostAsync()
{
if (!ModelState.IsValid)
{
return Page();
}
return RedirectToPage("MessageSent");
}
}
public class ContactMessageModel
{
[Required]
public string Name { get; set; }
[Required]
public string Email { get; set; }
[Required, CustomValidation]
public string Message { get; set; }
}
A test validation attribute class is as follows:
public class CustomValidationAttribute : ValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
return ValidationResult.Success;
}
}
The validation attribute is called for the ContactMessageModel.Message property, but it isn't called for ContactModel.SomeData property.
Why is this and how do I fix it?

Answer 1

I was running into this too. In my case my issue was because I missed the addition of the [BindProperty] attribute when I moved the properties from a wrapper class model into the PageModel directly. I see that's not the case for you.
In your case I do see that you have the [Required] attribute on all properties except the ContactModel.SomeData. Maybe adding [Required] there would get things acting as you would expect?