ViewModels

I've already given a lot of answers about it , but I did not mention the advantages in them, so I'll talk of some.

1. Variable Exposure Control

The approach is widely used when it is not desirable to expose the variables of a Model directly mapped to a database. The ViewModel acts as a data container that is handled by Controller , which can avoid some problems, such as inserting undue data into a database.

2. Organization of Forms

In many cases it is desirable for a form to have information that is common or divisible between two or more Models . The ViewModel , in addition to rationalizing the form, also hides the internal information structure.

3. Mounting Search Result Pages

This is one of my favorites. Imagine a search screen with filters (reposted by a form) and their results.

You can use a form that accepts the verb GET and accommodate a ViewModel both the search parameters used and the results of that search, in the form of a collection or list. For example:

namespace MeuProjeto.ViewModels
{
    public class ProcessoViewModel
    {
        [DisplayName("Formato de Saída dos Dados")]
        public FormatoSaidaDados SaidaDados { get; set; }

        [Column("DATA_ENTRADA")]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        [DisplayName("Data de Entrada Inicial")]
        public DateTime? DataEntradaInicial { get; set; }
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        [DisplayName("Data de Entrada Final")]
        public DateTime? DataEntradaFinal { get; set; }
        [Column("DT_DISTRIB")]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        [DisplayName("Data de Distribuição Inicial")]
        public DateTime? DataDistribuicaoInicial { get; set; }
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        [DisplayName("Data de Distribuição Final")]
        public DateTime? DataDistribuicaoFinal { get; set; }
        [Column("DATA_ENCERRAMENTO")]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        [DisplayName("Data de Encerramento Inicial")]
        public DateTime? DataEncerramentoInicial { get; set; }
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
        [DisplayName("Data de Encerramento Final")]
        public DateTime? DataEncerramentoFinal { get; set; }

        [Column("PASTA")]
        [DisplayName("Caso Inicial")]
        public int? PastaInicial { get; set; }
        [DisplayName("Caso Final")]
        public int? PastaFinal { get; set; }
        [Column("COD_CLIENTE")]
        [DisplayName("Cliente Inicial")]
        public int? ClienteIdInicial { get; set; }
        [DisplayName("Cliente Final")]
        public int? ClienteIdFinal { get; set; }

        [Column("COD_REGIONAL")]
        [DisplayName("Código da Regional")]
        public String RegionalId { get; set; }
        [Column("COD_REGIONAL")]
        [DisplayName("Regionais")]
        public String[] RegionalIdMultiple { get; set; }

        public virtual IEnumerable<Models.Processo> Resultados { get; set; }
    }
}

4. Serialization and Deserialization of JSON

Here is possibly where the purpose of your question best fits. Serialize in JSON using ViewModel is even more advantageous than using Model for three reasons:

• You can structure JSON using ViewModel , composing Models any way you like;
• Does not have the ASP.NET MVC Circular Reference problem

• Uses only a single command for serialization:

  return Json(meuViewModel, JsonRequestBehavior.AllowGet);