Entity Framework Code First DataAnnotations [MaxLength] and [MinLength] attributes
Example
[MaxLength(int)] attribute can be applied to a string or array type property of a domain class. Entity Framework will set the size of a column to the specified value.
using System.ComponentModel.DataAnnotations;
public class Person
{
public int PersonID { get; set; }
[MinLength(3), MaxLength(100)]
public string PersonName { get; set; }
}
The resulting column with the specified column length:
[MinLength(int)] attribute is a validation attribute, it does not affect the database structure. If we try to insert/update a Person with PersonName with length less than 3 characters, this commit will fail. We’ll get a DbUpdateConcurrencyException that we'll need to handle.
using (var db = new ApplicationDbContext())
{
db.Staff.Add(new Person() { PersonName = "ng" });
try
{
db.SaveChanges();
}
catch (DbEntityValidationException ex)
{
//ErrorMessage = "The field PersonName must be a string or array type with a minimum length of '3'."
}
}
Both [MaxLength] and [MinLength] attributes can also be used with asp.net-mvc as a validation attribute.
