c# - How to manually validate a model with attributes?

Question

I have a class called User and a property Name

public class User
{
    [Required]
    public string Name { get; set; }
}

And I want to validate it, and if there are any errors add to the controller's ModelState or instantiate another modelstate...

[HttpPost]
public ActionResult NewUser(UserViewModel userVM)
{
    User u = new User();
    u.Name = null;

    /* something */

    // assume userVM is valid
    // I want the following to be false because `user.Name` is null
    if (ModelState.IsValid)
    {
        TempData["NewUserCreated"] = "New user created sucessfully";

        return RedirectToAction("Index");
    }

    return View();
}

The attributes works for UserViewModel, but I want to know how to validate a class without posting it to an action.

How can I accomplish that?

Answer 1

You can use Validator to accomplish this.

var context = new ValidationContext(u, serviceProvider: null, items: null);
var validationResults = new List<ValidationResult>();

bool isValid = Validator.TryValidateObject(u, context, validationResults, true);