Retain a list of objects and pass it to the create/edit view when validation fails in ASP.NET MVC 2

Question

I am binding a Foreign key property in my model. I am passing a list of possible values for that property in my model. The model looks something like this:

public class UserModel
{
    public bool Email { get; set; }
    public bool Name { get; set; }
    public RoleModel Role { get; set; }
    public IList<RoleModel> Roles  { get; set; }
}

public class RoleModel
{
    public string RoleName
    {
        get;
        set;
    }
}

This is what I have in the controller:

public ActionResult Create()
{
    IList<RoleModel> roles = RoleModel.FromArray(_userService.GetAllRoles());
    UserModel model = new UserModel()
                      {
                          Roles = roles
                      };
    return View(model);
}

In the view I have:

<div class="editor-label">
        <%= Html.LabelFor(model => model.Role) %>
</div>
<div class="editor-field">
    <%= Html.DropDownListFor(model => model.Role, new SelectList(Model.Roles, "RoleName", "RoleName", Model.Role))%>
    <%= Html.ValidationMessageFor(model => model.Role)%>
</div>

What do I need to do to get the list of roles back to my controller to pass it again to the view when validation fails. This is what I need:

[HttpPost]
public ActionResult Create(UserModel model)
{
    if (ModelState.IsValid)
    {
        // insert logic here
    }
    //the validation fails so I pass the model again to the view for user to update data but model.Roles is null :(
    return View(model);
}

As written in the comments above I need to pass the model with the list of roles again to my view but model.Roles is null. Currently I ask the service again for the roles (model.Roles = RoleModel.FromArray(_userService.GetAllRoles());) but I don't want to add an extra overhead of getting the list from DB when I have already done that..

Anyone knows how to do it?

Answer 1

You could store it in TempData.

TempData["UserRoles"] = Model.Roles;

That said, I tend to shy away from keeping data between requests. Ask yourself seriously how much of a drain it would be to go back to the database.