EFCore Identity: Admin Razor Page : create user with roles - identity

Question

I'm trying to create a Razor Page for an admin to add a user with checkboxes to select the roles for the user. But i'm not getting the desired result.
Pagemodel:
[BindProperty(SupportsGet = true)]
public InputModel Input { get; set; }
public class InputModel
{
public string Email {get; set;}
...
public list<rol> rollen {get;set;}
}
public class rol
{
public string name {get;set}
public bool selected {get;set;}
}
In the OnGet():
Input.rollen = (from rol in _roleManager.Roles
select new rol
{
name = rol.Name,
selected = false
}).ToList();
In the Page:
#foreach (var rol in Model.Input.rollen.OrderBy(x=>x.name))
{
<div class="form-check">
<input class="form-check-input" type="checkbox" id="#rol.name" name="#rol.name">
<label class="form-check-label" for="#rol.name">
#rol.name
</label>
</div>
}
Visually it gives the correct result. But off course when posting the form, it doesn't match the model. What is the correct way of doing this? I could just add the checkboxes manually, one by one but that's not really the way of doing things

Answer 1

I found the answer using thins page: https://www.learnrazorpages.com/razor-pages/forms/checkboxes.
I added
[BindProperty]
public InputModel Input { get; set; }
[BindProperty]
public List<string> roles { get; set; }
Onget:
public void OnGet()
{
var rollen = _roleManager.Roles.OrderBy(x => x.Name).Select(x => x.Name).ToList();
ViewData["roles"] = roles;
}
On page:
<div class="form-row">
<label class="col-md-3 col-form-label">Rollen</label>
<div class="form-group col-md-9">
#foreach(var role in ViewData["roles"] as List<string>)
{
<div class="form-check">
<input class="form-check-input" type="checkbox" name="roles" value="#role">
<label class="form-check-label">
#role
</label>
</div>
}
</div>
</div>
On Post you get the List which contains all the checked values. It's important that all checkboxes have the same name-attribute
I found that page before but i just didn't get it to work. But that was because i added the List as part of the InputModel. I had to add it as Bindproperty separatly.