Problem when submit a form with select tag helper asp.net core 6 - asp.net-core

Question

I want to use select tag helper to choose a role for creating account in my web app.
The following is my code
[HttpGet]
public ActionResult Create()
{
var model = new AccountCreateViewModel()
{
Roles = new SelectList(_roleManager.Roles, "Id", "Name").ToList()
};
return View(model);
}
The following is the code in view of the select.
<div class="form-floating">
<select asp-for="RoleId" asp-items="#Model.Roles" class="form-select"></select>
<label asp-for="RoleId"></label>
<span asp-validation-for="RoleId" class="text-danger"></span>
</div>
<input type="submit" class="w-100 btn btn-lg btn-primary" />
The following is my model
public class AccountCreateViewModel
{
public RegisterModel.InputModel Input { get; set; } = new();
[StringLength(50)]
[Required]
public string FullName { get; set; }
[DataType(DataType.Date)]
public DateTime? BirthDate { get; set; } = null;
[StringLength(80)]
public string Address { get; set; }
[Required]
[Display(Name = "Role")]
public string RoleId { get; set; }
public List<SelectListItem> Roles { get; set; }
}
However, after I submit the form, then the controller check the model state, and it is invalid. I have debugged and all the fields is valid except Roles.
So, someone can give me a solution for this situation?
model state debugging

Answer 1

Apply [ValidateNever] attribute to remove validate of the Roles on the server side. When applied to a property, the validation system excludes that property.
public class AccountCreateViewModel
{
...
[ValidateNever]
public List<SelectListItem> Roles { get; set; }
}

Answer 2

Consider that a SelectList takes an object of type IEnumerable as the first argument in the constructor. Make sure that you give it an IEnumerable or List in this section:
Roles = new SelectList(_roleManager.Roles, "Id", "Name").ToList()
This code may help you:
Roles = new SelectList(_roleManager.Roles.ToList(), "Id", "Name")
If _roleManager.Roles returns an IEnumerable or List, you don't need the .ToList()