ASP.NET - Como validar una clase usada en varios formularios que utilizan diferentes campos

// Accion Registrar

if(myModel.Prop1 != myName)

{

    ModelState.AddModelError("Prop1", No coincide con nombre de usuario");

}

// en Otra accion prop1 ==  cadena vacia

if(myModel.Prop1 !=string.Emty)

{

    ModelState.AddModelError("Prop1", ""debe ser una cadena vacia");

}

using NPoco;

using System;

using System.ComponentModel;

using System.ComponentModel.DataAnnotations;

namespace Entidades

{

    [TableName("Clientes")]

    [PrimaryKey("Id")]

    public class Cliente

    {

        [Required]

        public Int32 Id { get; set; }

        [DisplayName("Start Date")]

        public DateTime FechaAlta { get; set; } = DateTime.Now;

        [DisplayName("Name")]

        [Required(ErrorMessage = "Name is required")]

        [StringLength(50, MinimumLength = 5, ErrorMessage = "Name cannot be longer than 50 characters and less than 5 characters")]

        public String Nombre { get; set; }

        [DisplayName("Address")]

        [Required(ErrorMessage = "Address is required")]

        [StringLength(30, MinimumLength = 5, ErrorMessage = "Address cannot be longer than 30 characters and less than 5 characters")]

        public String Domicilio { get; set; }

        [DisplayName("Zip Code")]

        [StringLength(8, MinimumLength = 0, ErrorMessage = "Zip Code cannot be longer than 8 characters")]

        public String CodPostal { get; set; }

        [DisplayName("City")]

        [Required(ErrorMessage = "City is required")]

        public Int32? IdCiudad { get; set; }

        [DisplayName("Phone")]

        [StringLength(15, MinimumLength = 0, ErrorMessage = "Phone cannot be longer than 15 characters")]

        public String Telefono { get; set; }

        [StringLength(15, MinimumLength = 0, ErrorMessage = "Fax cannot be longer than 15 characters")]

        public String Fax { get; set; }

        [DisplayName("Contact")]

        [StringLength(45, MinimumLength = 0, ErrorMessage = "Contact cannot be longer than 45 characters")]

        public String Contacto { get; set; }

        [DisplayName("Email")]

        [RegularExpression("^[a-zA-Z0-9_\\.-]+@([a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,6}$", ErrorMessage = "Email is invalid")]

        [StringLength(60, MinimumLength = 0, ErrorMessage = "Email cannot be longer than 60 characters")]

        public String Correo { get; set; }

        [DisplayName("Credit Limit")]

        public Decimal LimiteCredito { get; set; } = 0;

        public Boolean Status { get; set; } = true;

        [Reference(ReferenceType.OneToOne, ColumnName = "IdCiudad", ReferenceMemberName = "Id")]

        public Ciudad Ciudad { get; set; }

    }

}