c# - liste de Checkbox dans ASP.NET MVC. Je ne peux pas récupérer les données d'une liste - Stack Overflow ou IEnumerable

I have a problem with an application using ASP.NET MVC 4, I'm trying to show in a view to create an entity called CompositePiece, a List of items (which are CompositePieces too) from my database, then, the user could select one or more of them, and the items selected would be in a collection in the 'father' CompositePiece, at first, my class CompositePiece:

namespace Garbi.Models{
  public class CompositePiece
    {
    [Key]
    public int CompositePieceId { get; set; }

    [Required(ErrorMessage = "Introduzca un nombre para la pieza")]
    [Display(Name = "Nombre de la pieza")]
    public string CompositePieceName { get; set; }

    public virtual ICollection<CompositePiece> Components { get; set; }

    public int ProcessId { get; set; }
    public int LevelOfHierarchy { get; set; }

    public CompositePiece(PieceModel model)
    {
        this.Components = new List<CompositePiece>();
        this.CompositePieceName = model.PieceModelName;
        LevelOfHierarchy = 0;
    }

    public CompositePiece()
    {
        this.Components = new List<CompositePiece>();
        LevelOfHierarchy = 0;
    }

    public CreateOrEditCompositePieceViewModel ToCreateOrEditCompositePieceViewModel(string processName)
    {
        return new CreateOrEditCompositePieceViewModel
        {
            CompositePieceName = this.CompositePieceName,
            ProcessId = this.ProcessId,
            ProcessName = processName
        };
      }
    }
  }

I have created a ViewModel to pass the data to a view, the ViewModel is:

namespace Garbi.ViewModels.CompositePieces
{
  public class CreateOrEditCompositePieceViewModel
  {

    [Required(ErrorMessage = "Introduzca un nombre para la pieza")]
    [Display(Name = "Nombre de la pieza")]
    public string CompositePieceName { get; set; }

    public virtual IEnumerable<SelectListItem> Components { get; set; }
    public string[] SelectedComponentsId { get; set; }

    public int ProcessId { get; set; }
    public string ProcessName { get; set; }

    public int LevelOfHierarchy { get; set; }

    public void AddComponentsList(IEnumerable<CompositePiece> dataProvider, CompositePiece fatherPiece)
    {
        List<SelectListItem> auxList = new List<SelectListItem>();
        foreach (CompositePiece piece in dataProvider)
        {
            SelectListItem item = new SelectListItem
            {
                Text=piece.CompositePieceName,
                Value = piece.CompositePieceId.ToString(),
                Selected = fatherPiece.Components.Contains(piece)
            };
            auxList.Add(item);
        }
        Components = new List<SelectListItem>(auxList);
    }

    public CompositePiece ToCompositePiece()
    {
        return new CompositePiece
        {
            CompositePieceName = this.CompositePieceName,
            LevelOfHierarchy = this.LevelOfHierarchy,
            ProcessId = this.ProcessId
        };
    }
  }
}

Mi View is:

@model Garbi.ViewModels.CompositePieces.CreateOrEditCompositePieceViewModel

@{
    ViewBag.Title = "Crear pieza compuesta";
 }

<div class="advertise">Crear pieza compuesta para @Model.ProcessName</div>

@using (Html.BeginForm()) {
  @Html.AntiForgeryToken()
  @Html.ValidationSummary(true)

  <fieldset>
    <legend>Nueva pieza compuesta</legend>


    <div class="editor-label">
        @Html.LabelFor(model => model.CompositePieceName)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.CompositePieceName)
        @Html.ValidationMessageFor(model => model.CompositePieceName)
    </div>
    <div class="editor-field">
        @foreach (var item in Model.Components)
        {
            <div class="checkbox">
                @Html.CheckBoxFor(i => item.Selected, item.Value)
                @Html.HiddenFor(i => item.Value)
                @item.Text
                @Html.HiddenFor(i => item)
            </div>
        }
    </div>

    @Html.HiddenFor(model => model.Components)
    @Html.HiddenFor(model => model.LevelOfHierarchy)
    @Html.HiddenFor(model => model.ProcessId)
    @Html.HiddenFor(model => model.ProcessName)

    <p>
        <input type="submit" value="Crear" />
    </p>
</fieldset>

<div class="back">
    @Html.NavLink("Process_"+@Model.ProcessId, "Page1", "Volver")
</div>
}

And at last, I want to show you the methods of my controller, they are:

public ActionResult ComposePieces(int processId)
    {
        context = new EFDbContext();
        Process process = context.ProcessesPaginable.FindEntityById(processId);
        CreateOrEditCompositePieceViewModel model = new CreateOrEditCompositePieceViewModel
        {
            ProcessId = process.ProcessId,
            ProcessName = process.ProcessName,
            LevelOfHierarchy = 0
        };
        IEnumerable<CompositePiece> totalPieces = context.CompositePiecesPaginable.FindAllCompositePiecesOfAProcess(processId).Where(p => p.LevelOfHierarchy == 0);
        model.AddComponentsList(totalPieces, model.ToCompositePiece());
        return View(model);
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult ComposePieces(CreateOrEditCompositePieceViewModel model)
    {
        context = new EFDbContext();
        CompositePiece compositePieceToAdd = model.ToCompositePiece();
        CompositePiece aux;
        [...]
    }

My problem comes when I call the view, I can see perfectly the collection of items, each of them with its checkbox, but when I check some of them, put the CompositePiece's name and click at Submit button, I recover the new CreateOrEditCompositePieceViewModel with its new name, but my attribute Components is empty. I think I am having a mistake of base, but I don't know where is the error, and why I have this problem.

Thank you for your time and sorry for my bad english.

I have a problem with an application using ASP.NET MVC 4, I'm trying to show in a view to create an entity called CompositePiece, a List of items (which are CompositePieces too) from my database, then, the user could select one or more of them, and the items selected would be in a collection in the 'father' CompositePiece, at first, my class CompositePiece:

namespace Garbi.Models{
  public class CompositePiece
    {
    [Key]
    public int CompositePieceId { get; set; }

    [Required(ErrorMessage = "Introduzca un nombre para la pieza")]
    [Display(Name = "Nombre de la pieza")]
    public string CompositePieceName { get; set; }

    public virtual ICollection<CompositePiece> Components { get; set; }

    public int ProcessId { get; set; }
    public int LevelOfHierarchy { get; set; }

    public CompositePiece(PieceModel model)
    {
        this.Components = new List<CompositePiece>();
        this.CompositePieceName = model.PieceModelName;
        LevelOfHierarchy = 0;
    }

    public CompositePiece()
    {
        this.Components = new List<CompositePiece>();
        LevelOfHierarchy = 0;
    }

    public CreateOrEditCompositePieceViewModel ToCreateOrEditCompositePieceViewModel(string processName)
    {
        return new CreateOrEditCompositePieceViewModel
        {
            CompositePieceName = this.CompositePieceName,
            ProcessId = this.ProcessId,
            ProcessName = processName
        };
      }
    }
  }

I have created a ViewModel to pass the data to a view, the ViewModel is:

namespace Garbi.ViewModels.CompositePieces
{
  public class CreateOrEditCompositePieceViewModel
  {

    [Required(ErrorMessage = "Introduzca un nombre para la pieza")]
    [Display(Name = "Nombre de la pieza")]
    public string CompositePieceName { get; set; }

    public virtual IEnumerable<SelectListItem> Components { get; set; }
    public string[] SelectedComponentsId { get; set; }

    public int ProcessId { get; set; }
    public string ProcessName { get; set; }

    public int LevelOfHierarchy { get; set; }

    public void AddComponentsList(IEnumerable<CompositePiece> dataProvider, CompositePiece fatherPiece)
    {
        List<SelectListItem> auxList = new List<SelectListItem>();
        foreach (CompositePiece piece in dataProvider)
        {
            SelectListItem item = new SelectListItem
            {
                Text=piece.CompositePieceName,
                Value = piece.CompositePieceId.ToString(),
                Selected = fatherPiece.Components.Contains(piece)
            };
            auxList.Add(item);
        }
        Components = new List<SelectListItem>(auxList);
    }

    public CompositePiece ToCompositePiece()
    {
        return new CompositePiece
        {
            CompositePieceName = this.CompositePieceName,
            LevelOfHierarchy = this.LevelOfHierarchy,
            ProcessId = this.ProcessId
        };
    }
  }
}

Mi View is:

@model Garbi.ViewModels.CompositePieces.CreateOrEditCompositePieceViewModel

@{
    ViewBag.Title = "Crear pieza compuesta";
 }

<div class="advertise">Crear pieza compuesta para @Model.ProcessName</div>

@using (Html.BeginForm()) {
  @Html.AntiForgeryToken()
  @Html.ValidationSummary(true)

  <fieldset>
    <legend>Nueva pieza compuesta</legend>


    <div class="editor-label">
        @Html.LabelFor(model => model.CompositePieceName)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.CompositePieceName)
        @Html.ValidationMessageFor(model => model.CompositePieceName)
    </div>
    <div class="editor-field">
        @foreach (var item in Model.Components)
        {
            <div class="checkbox">
                @Html.CheckBoxFor(i => item.Selected, item.Value)
                @Html.HiddenFor(i => item.Value)
                @item.Text
                @Html.HiddenFor(i => item)
            </div>
        }
    </div>

    @Html.HiddenFor(model => model.Components)
    @Html.HiddenFor(model => model.LevelOfHierarchy)
    @Html.HiddenFor(model => model.ProcessId)
    @Html.HiddenFor(model => model.ProcessName)

    <p>
        <input type="submit" value="Crear" />
    </p>
</fieldset>

<div class="back">
    @Html.NavLink("Process_"+@Model.ProcessId, "Page1", "Volver")
</div>
}

And at last, I want to show you the methods of my controller, they are:

public ActionResult ComposePieces(int processId)
    {
        context = new EFDbContext();
        Process process = context.ProcessesPaginable.FindEntityById(processId);
        CreateOrEditCompositePieceViewModel model = new CreateOrEditCompositePieceViewModel
        {
            ProcessId = process.ProcessId,
            ProcessName = process.ProcessName,
            LevelOfHierarchy = 0
        };
        IEnumerable<CompositePiece> totalPieces = context.CompositePiecesPaginable.FindAllCompositePiecesOfAProcess(processId).Where(p => p.LevelOfHierarchy == 0);
        model.AddComponentsList(totalPieces, model.ToCompositePiece());
        return View(model);
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult ComposePieces(CreateOrEditCompositePieceViewModel model)
    {
        context = new EFDbContext();
        CompositePiece compositePieceToAdd = model.ToCompositePiece();
        CompositePiece aux;
        [...]
    }

My problem comes when I call the view, I can see perfectly the collection of items, each of them with its checkbox, but when I check some of them, put the CompositePiece's name and click at Submit button, I recover the new CreateOrEditCompositePieceViewModel with its new name, but my attribute Components is empty. I think I am having a mistake of base, but I don't know where is the error, and why I have this problem.

Thank you for your time and sorry for my bad english.

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