MVC Dropdown list from a froma different Model

Question

I'm trying to create a dropdown on my View that populates all the usernames specified in a different table.

I've tried the tuple route but it doesn't seem to be working for me. Also looked into adding a model containing both models (Users and Tasks)

View

@model Tuple<Task,User>

@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>


@using (Html.BeginForm()) 
{
    @Html.AntiForgeryToken()

    <div class="form-horizontal">
        <h4>Task</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.Item1.Name, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Item1.Name, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Item1.Name, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Item1.Details, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Item1.Details, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Item1.Details, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Item1.StartDate, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Item1.StartDate, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Item1.StartDate, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Item1.EndDate, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Item1.EndDate, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Item1.EndDate, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Item1.AssignedTo, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor()
                @Html.ValidationMessageFor(model => model.Item1.AssignedTo, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </div>
    </div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

Controller

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Net;
using System.Web;
using System.Web.Mvc;
using Base.Models;
using PagedList;

namespace Base.Controllers
{
    public class UsersController : Controller {
        private WebDBEntities db = new WebDBEntities();

        // GET: Users
        public ActionResult Index(string sortOrder,string currentFilter, string searchString,int? page) {
            ViewBag.NameSortParam = string.IsNullOrEmpty(sortOrder) ? "name_desc" : "";
            ViewBag.SurnameSortParam = sortOrder == "Surname" ? "surname_desc" : "Surname";
            ViewBag.TeamSortParam = sortOrder == "Team" ? "team_desc" : "Team";
            if(searchString != null) {
                page = 1;
                } else {
                searchString = currentFilter;
                }

            ViewBag.CurrentFilter = searchString;
            var users = from u in db.Users select u;
            if (!string.IsNullOrEmpty(searchString)) {
                users = users.Where(u => u.Name.Contains(searchString) || u.Surname.Contains(searchString));
                }
            switch (sortOrder) {
                case "name_desc":
                    users = users.OrderByDescending(u => u.Name);
                    break;
                case "Team":
                    users = users.OrderBy(u => u.Team);
                    break;
                case "team_desc":
                    users = users.OrderByDescending(u => u.Team);
                    break;
                case "Surname":
                    users = users.OrderBy(u => u.Surname);
                    break;
                case "surname_desc":
                    users = users.OrderByDescending(u => u.Surname);
                    break;
                default:
                    users = users.OrderBy(u => u.Name);
                    break;
                }
            int pageSize = 10;
            int pageNumber = (page ?? 1);
            return View(users.ToPagedList(pageNumber,pageSize));
            }


        // GET: Users/Details/5
        public ActionResult Details(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            User user = db.Users.Find(id);
            if (user == null)
            {
                return HttpNotFound();
            }
            return View(user);
        }

        // GET: Users/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Users/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "ID,Name,Surname,Team,UserName")] User user)
        {
            if (ModelState.IsValid)
            {
                user.UserName = string.Format("{0}{1}", user.Name.Substring(0, 1), user.Surname); 
                db.Users.Add(user);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(user);
        }

        // GET: Users/Edit/5
        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            User user = db.Users.Find(id);
            if (user == null)
            {
                return HttpNotFound();
            }
            return View(user);
        }

        // POST: Users/Edit/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit([Bind(Include = "ID,Name,Surname,Team,UserName")] User user)
        {
            if (ModelState.IsValid)
            {
                db.Entry(user).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(user);
        }

        // GET: Users/Delete/5
        public ActionResult Delete(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            User user = db.Users.Find(id);
            if (user == null)
            {
                return HttpNotFound();
            }
            return View(user);
        }

        // POST: Users/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public ActionResult DeleteConfirmed(int id)
        {
            User user = db.Users.Find(id);
            db.Users.Remove(user);
            db.SaveChanges();
            return RedirectToAction("Index");
        }


        public ActionResult ViewUserTasks(string Username) {
            return View("UserTasks",db.Tasks.Where(uu => uu.AssignedTo == Username));
            }

        public ActionResult GetAllUsers() {
            List<string> users = new List<string>();
            foreach (var item in db.Users) {
                users.Add(item.UserName.ToString())
                }
            return View(users);
            }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                db.Dispose();
            }
            base.Dispose(disposing);
        }
    }
}

Any assistance would be great, thanks in advance.