ListBoxFor is not fully updating the viewmodel on submit

Question

I have been able to create viewmodel like this (please ignore that it includes another viewmodel, that will be fixed after I solve my current problem :) ):

public class UserViewModel
{
    #region Variables
    private SecUserViewModel user;
    private string[] assignedRolesIds;
    private List<SecRoleViewModel> availableRoles;
    #endregion

    #region Properties
    public SecUserViewModel User 
    { 
        get { return this.user; }
        set { this.user = value; }

    }
    public string Guid
    {
        get { return this.user.Guid.ToString(); }
        set { this.user.Guid = value; }
    }

    public string UserName
    {
        get { return this.user.UserName; }
        set { this.user.UserName = value; }
    }

    public string Email
    {
        get { return this.user.Email; }
        set { this.user.Email = value; }
    }

    public byte[] AuthDigest
    {
        get { return this.user.AuthDigest; }
        set { this.user.AuthDigest = value; }
    }

    public bool IsUsingTempPasswd
    {
        get { return this.user.IsUsingTempPasswd; }
        set { this.user.IsUsingTempPasswd = value; }
    }
    public DateTime? LastLogin
    {
        get { return this.user.LastLogin; }
        set { this.user.LastLogin = value; }
    }

    public DateTime? PasswordChanged
    {
        get { return this.user.PasswordChanged; }
        set { this.user.PasswordChanged = value; }
    }
    public string[] AssignedRolesIds
    {
        get { return this.assignedRolesIds; }
        set { this.assignedRolesIds = value; }

    }
    public List<SecRoleViewModel> AvailableRoles
    {
        get { return this.availableRoles; }
        set { this.availableRoles = value; }

    }
    #endregion

    #region Constructor

    public UserViewModel()
    {
        User = new SecUserViewModel();
        AssignedRolesIds = null;
        AvailableRoles = new List<SecRoleViewModel>(0);
    }

    public UserViewModel(SecUserViewModel secUser, List<SecRoleViewModel> roleList, List<SecRoleViewModel> availableList)
    {
        User = secUser;
        AssignedRolesIds = roleList.Select(r => r.Role.Guid.ToString()).ToArray();
        AvailableRoles = availableList;
    }

    #endregion
}

My controller has an edit action. On "GET" I pass viewmodel and it is displayed properly including the multiselect list and preselected values. But when I "POST" the "Edit", UserViewModel that is passed back has "AssignedRolesIds" and "AvailableRoles" Empty, although everything else is filled. When I check FormCollection object, there are "AssignedRolesIds" present as a key.

My view looks like this:

@model DocuLive.ViewModels.UserViewModel

@{
    ViewBag.Title = "Edit";
    Layout = "~/Views/Shared/_AdminPage.cshtml";
}

<h2>Edit</h2>
<div class="error-message">@TempData["Fail"]</div>
<div class="success-message">@TempData["Success"]</div>
@using (Html.BeginForm("Edit", "User", FormMethod.Post))
{
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>SecUser</legend>

        <div class="editor-label">
            @Html.LabelFor(model => model.User.Guid)
        </div>
        <div class="editor-field">
            @Html.DisplayFor(model => model.User.Guid)
            @Html.HiddenFor(model => model.User.Guid)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.User.UserName)
        </div>
        <div class="editor-field">
            @Html.DisplayFor(model => model.User.UserName)
            @Html.HiddenFor(model => model.User.UserName)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.User.Email)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.User.Email)
            @Html.ValidationMessageFor(model => model.User.Email)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.User.IsUsingTempPasswd)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.User.IsUsingTempPasswd)
            @Html.ValidationMessageFor(model => model.User.IsUsingTempPasswd)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.User.LastLogin)
        </div>
        <div class="editor-field">
            @Html.DisplayFor(model => model.User.LastLogin)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.User.PasswordChanged)
        </div>
        <div class="editor-field">
            @Html.DisplayFor(model => model.User.PasswordChanged)
        </div>
        <div class="hidden-field">
            @Html.HiddenFor(model => model.User.AuthDigest)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.AssignedRolesIds)
        </div>
        <div class="editor-field">
            @Html.ListBoxFor(x => x.AssignedRolesIds, new MultiSelectList(Model.AvailableRoles, "Guid", "RoleName"), new { Multiple = "multiple", @class = "multi-select-list" }) 
        </div>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Users")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

Can anyone advise why only values related to ListBoxFor are not passed back (there is a null value)?

Thanks in advance

Answer 1

It seems that the problem is binding the string array values to string id value of complex object (in my case Role) - but I figured out a way around it eventually. The trick is to have this signature of the method:

[HttpPost]
public ActionResult Edit(UserViewModel user, string [] assignedRolesIds)

And then you have this in view:

@Html.ListBox("AssignedRolesIds",new MultiSelectList(Model.AvailableRoles, "Guid", "RoleName"),new { Multiple = "multiple", @class = "multi-select-list"})

With this solution, you have to reassign "assignedRolesIds" back to "AssignedRolesIds" property on UserViewModel, but that is only two lines (including check that the array is not emppty or null).