اعتبار سنجی مقادیر Enum

namespace Model
{
    public enum MyEnum
    {
        None = 1000,
        Value1 = 2000,
        Value1 = 3000
    }

    public class NotNoneAttribute : ValidationAttribute
    {
        public override bool IsValid(object value)
        {
            if (value is MyEnum enu)
            {
                return Enum.IsDefined(typeof(MyEnum), enu);
            }

            return false;
        }

        public override string FormatErrorMessage(string name)
        {
            return $"The field {name} cannot be set to the default value. Please choose a valid MyEnum.";
        }
    }
}

[Required]
[NotNone]
public MyEnum MyEnum { get; set; }