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c# - Passing an array of ids from view pages to controller

I discovered that the ids are not getting passed through from the razor page to the controller. So my int[] userIds is empty but I don't know why or how to fix it. Please help.

Below is my code.

Account Controller:

public class AccountController : Controller
{
    private readonly UserManager<ApplicationUser> _userManager;

    private readonly SignInManager<ApplicationUser> _signInManager;

    private readonly RoleManager<Role> _roleManager;

    public AccountController(UserManager<ApplicationUser> userManager, SignInManager<ApplicationUser> signInManager, RoleManager<Role> roleManager)
    {
        _userManager = userManager;
        _signInManager = signInManager;
        _roleManager = roleManager;
    }

    public IActionResult Remove()
    {
        var users = _userManager.Users.OrderBy(o=> o.LastName).ToList();
        RemoveViewModel removeViewModel = new RemoveViewModel(users);
        return View(removeViewModel);
    }

    [HttpPost]
    public IActionResult Remove(int[] userIds)
    {

        if (userIds == null || userIds.Length==0)
        { 
            throw new System.ArgumentException("Array is empty", "original");
        }

        return Redirect("/Home/Index");
    }

view:

    @model WebApplication1.ViewModels.RemoveViewModel
<html>
<body>
    <form asp-controller="Account" asp-action="Remove" method="post">

            @foreach (var item in Model.Users)
            {
            <div>
                <label> @item.FirstName @item.LastName</label>
                <input type="checkbox" id="@item.Id" value="@item.Id" />
            </div>
            }


        <input type="submit" value=" Remove User" /><br>

    </form>

    </body>
</html>

ViewModel:

    namespace WebApplication1.ViewModels
{
    public class RemoveViewModel
    {
        public List<ApplicationUser> Users { get; set; }

        public RemoveViewModel(List<ApplicationUser> users)
        {
            Users = users; 
        }
    }
}
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by (71.8m points)

The model binding in Asp.Net MVC is done by the name attribute of the html elements. So, add the name attribute to the input with the value of userIds. Hence, multiple elements with one name will bind to a single parameter of the same name that results in a list:

<input name="userIds" type="checkbox" id="@item.Id" value="@item.Id" />

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