I'm getting code first approach validation error can you help me

Question

I add error massege and I update database with (datanase-update -Force).but not working error massege. why ?

Answer 1

Hi @Harun Ergün,

You want to implement model validation, do you use the ValidationMessageFor attribute in the View?

@Html.ValidationMessageFor(model => model.StudentName, "", new { @class = "text-danger" })

You can refer to the following examples to see where your code is missing.

public class HomeController : Controller
    {
        
        private SchoolContext db = new SchoolContext();
        public ActionResult Index()
        {           
            return View(db.Students.ToList());
        }
        public ActionResult Edit(int Id)
        {         
            var std = db.Students.ToList().Where(s => s.StudentId == Id).FirstOrDefault();
            return View(std);
        }
        [HttpPost]
        public ActionResult Edit(Student std)
        {           
            var student = db.Students.ToList().Where(s => s.StudentId == std.StudentId).FirstOrDefault();
            student.StudentName = std.StudentName;
            db.SaveChanges();

            return RedirectToAction("Index");
        }
    }

 public class Student
    {
        public int StudentId { get; set; }
        [Column(TypeName = "Varchar")]
        [StringLength(30, ErrorMessage = "error")]
        public string StudentName { get; set; }
        public int Age { get; set; }
    }

You can also iterate over each error in the Catch loop to find out where the error is. code show as below:

try
{
    db.SaveChanges();
}
catch (DbEntityValidationException ex)
{
    foreach (var entityValidationErrors in ex.EntityValidationErrors)
    {
        foreach (var validationError in entityValidationErrors.ValidationErrors)
        {
            Response.Write("Property: " + validationError.PropertyName + " Error: " + validationError.ErrorMessage);
        }
    }
}

Best regards,
Lan Huang

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