创建新用户时添加角色

Question

With the following code I managed to add a dropdown field to the create user page where a role can be assigned when creating a new user. I have done this using a ViewBag but I feel like this isn't the most elegant solution, so I'm trying to change it by using a List<SelectListItem> RolesList in my CreateUserViewModel . This way I could get rid of the ViewBags

I'm not sure how to approach this as I'm still new to ViewModels, I've commented out my current solution in the HttpPost Create() method. Any help would be greatly appreciated!

AccountController.cs

    [HttpGet]
    public ActionResult Create()
    {
        List<SelectListItem> list = new List<SelectListItem>();

        foreach (var role in roleManager.Roles)
        {
            list.Add(new SelectListItem(){Value = role.Name, Text = role.Name});
        }

        ViewBag.Roles = list;
        return View();
    }

    [HttpPost]
    public async Task<IActionResult> Create(CreateUserViewModel user)
    {
        // var UserList = user.RolesList;
        // foreach (var role in roleManager.Roles)
        // {
        //  UserList.Add(new SelectListItem(){Value = role.Name, Text = role.Name});
        // }

        List<SelectListItem> list = new List<SelectListItem>();

        foreach (var role in roleManager.Roles)
        {
            list.Add(new SelectListItem() { Value = role.Name, Text = role.Name });
        }
        ViewBag.Roles = list;
        if (ModelState.IsValid)
        {
            var appUser = new ApplicationUser
            {
                UserName = user.Name,
                Email = user.Email
            };
            var result = await userManager.CreateAsync(appUser, user.Password);
            if (result.Succeeded)
            {
                await userManager.AddToRoleAsync(appUser, user.RoleName);

                return RedirectToAction("Index");
            }
        }
        return View(user);
    }

CreateUserViewModel.cs

public class CreateUserViewModel
{
    [Required]
    public string Name { get; set; }

    [Required]
    [DataType(DataType.Password)]
    public string Password { get; set; }

    [Display(Name = "Select Role")]
    public string RoleName { get; set; }

    public List<SelectListItem> RolesList { get; set; }

Create.cshtml

@model ViewModels.CreateUserViewModel
  
<h1>Create User</h1>

<a asp-action="Index" class="btn btn-secondary">Back</a>
<div asp-validation-summary="All" class="text-danger"></div>
  
<form method="post">
    <div class="form-group">
        <label asp-for="Name"></label>
        <input asp-for="Name" class="form-control" />
    </div>
    <div class="form-group">
        <label asp-for="Password"></label>
        <input asp-for="Password" class="form-control" />
    </div>
    <div class="form-group">
        //@Html.DropDownListFor(m => m.RoleName, new SelectList(Model.RolesList, "Value", "Text"), new { @class = "form-control" })
        @Html.DropDownListFor(m => m.RoleName, new SelectList(ViewBag.Roles,"Value", "Text"), new { @class = "form-control"})
    </div>
    <button type="submit" class="btn btn-primary">Create</button>
</form>

Answer 1

If you initialize your view model in the get method and return it to the view, then you can simply avoid the viewbag. Although we can do some optimization to the code to avoid db hits, but something like this should work.

[HttpGet]
        public ActionResult Create()
        {
            List<SelectListItem> list = new List<SelectListItem>();

            foreach (var role in roleManager.Roles)
            {
                list.Add(new SelectListItem() { Value = role.Name, Text = role.Name });
            }


            ViewBag.Roles = list; // this we can eliminate now !

            return View(new CreateUserViewModel
            {
                RolesList = list // this should populate the dropdown in your example
            });

        }