ctx.SaveChanges（）如何影响返回View（＆＃34; Action＆＃34;，model）vs return RedirectToAction（＆＃34; Action＆＃34;）

Question

我有一个带有两个动作的控制器。一个操作只是更新数据库的帖子。另一种是视图模型。但是，在我更新数据库的操作中，我将其返回到具有视图模型的原始视图。

public ActionResult ManageMxieUsers()
        {

            var model = from el in aphdb.view_EmployeeList
                        join p in aphdb.MxieCallRevPermissions on el.Id equals p.AspNetUserUserID into gj
                        from sub in gj.DefaultIfEmpty()
                        select new vm_ManageMxieUsers { Id = el.Id, UserName = el.UserName, PermissionLevel = sub.PermissionLevel, MxieCallRevPermCustomList = aphdb.MxieCallRevPermCustomList.Where(w => w.PermissionID == sub.PermissionID ) };

            ViewBag.EmployeeList = aphdb.view_EmployeeList.OrderBy(o => o.UserName);

            return View(model);
        }

这部分完美无缺。

这是我的帖子方法：

[HttpPost]
        public ActionResult ManageMxieUsers(string userID, Int16 permissionLevel, List<string> customUserList)
        {
            var UserToEdit = aphdb.MxieCallRevPermissions.Where(w => w.AspNetUserUserID == userID).FirstOrDefault();

            if (UserToEdit == null)
            {
                MxieCallRevPermissions addPerm = new MxieCallRevPermissions();

                addPerm.AspNetUserUserID = userID;
                addPerm.PermissionLevel = permissionLevel;

                aphdb.MxieCallRevPermissions.Add(addPerm);
                aphdb.SaveChanges();

                if (permissionLevel == 3)
                {
                    foreach (var id in customUserList)
                    {
                        MxieCallRevPermCustomList list = new MxieCallRevPermCustomList();

                        list.PermissionID = addPerm.PermissionID;
                        list.AspNetUserID = id;

                        aphdb.MxieCallRevPermCustomList.Add(list);

                    }
                }

                aphdb.SaveChanges();

                @ViewBag.Success = true;
            }
            else
            {
                UserToEdit.PermissionLevel = permissionLevel;

                aphdb.SaveChanges();

                if (permissionLevel == 3)
                {
                    // Remove old custom list
                    var customList = aphdb.MxieCallRevPermCustomList.Where(w => w.PermissionID == UserToEdit.PermissionID).ToList();
                    aphdb.MxieCallRevPermCustomList.RemoveRange(customList);
                    aphdb.SaveChanges();

                    foreach (var id in customUserList)
                    {
                        MxieCallRevPermCustomList list = new MxieCallRevPermCustomList();

                        list.PermissionID = UserToEdit.PermissionID;
                        list.AspNetUserID = id;

                        aphdb.MxieCallRevPermCustomList.Add(list);

                    }

                    aphdb.SaveChanges();
                }
                else
                {
                    // Remove old custom list
                    var customList = aphdb.MxieCallRevPermCustomList.Where(w => w.PermissionID == UserToEdit.PermissionID).ToList();
                    aphdb.MxieCallRevPermCustomList.RemoveRange(customList);
                    aphdb.SaveChanges();
                }

                aphdb.SaveChanges();

                @ViewBag.Success = true;
            }

            //aphdb.SaveChangesAsync(); // Testing ot make sure SaveChanges fired before this code.

            var model = from el in aphdb.view_EmployeeList
                        join p in aphdb.MxieCallRevPermissions on el.Id equals p.AspNetUserUserID into gj
                        from sub in gj.DefaultIfEmpty()
                        select new vm_ManageMxieUsers { Id = el.Id, UserName = el.UserName, PermissionLevel = sub.PermissionLevel, MxieCallRevPermCustomList = aphdb.MxieCallRevPermCustomList.Where(w => w.PermissionID == sub.PermissionID) };

            ViewBag.EmployeeList = aphdb.view_EmployeeList.OrderBy(o => o.UserName);

            //return RedirectToAction("ManageMxieUsers"); // WORKS
            return View("ManageMxieUsers", model); // ERROR NULL on AspNetUser
        }

现在我只是return View("ManageMxieUsers", model);错误回来说AspNetUsers为空。但是，当我重新加载此页面时，它工作得很好。当我return RedirectToAction("ManageMxieUsers");时，我没有收到任何错误，但当然我丢失了ViewBag。

我唯一的猜测是aphdb.SaveChanges()没有立即反映出来？即便如此，我也可以对数据库执行SQL查询，并确实已经添加/更新了数据。正如重新加载当前页面所引用的那样。

所以我不知道为什么在这个post方法中我的视图模型部分会出现空条目，但是当我重新加载它时，它们会正常填充。

我可以将其保留为RedirectToAction，但我想更好地理解为什么这种行为能够使其发挥作用。

这是打破

的视图部分

<tbody>
    @{ int? permissionLevel; }
    @foreach (var user in Model)
    {
        permissionLevel = user.PermissionLevel ?? 4;
        <tr>
            <td>@user.Id</td>
            <td>
                <a href="#" class="mr5 selectUser" data-toggle="modal" data-userid="@user.Id" data-username="@user.UserName" data-permissionlevel="@user.PermissionLevel" data-target=".bs-example-modal-panel">@user.UserName</a>
            </td>
            <td>@permissionLevel</td>
            <td>
                @foreach (var customUser in user.MxieCallRevPermCustomList)
                {
                    @("[" + customUser.AspNetUsers.FirstName + " " + customUser.AspNetUsers.Lastname + "] ")
                }
            </td>
        </tr>
    }
</tbody>

在我的customUser.AspNetUsers = null方法中使用return View("ManageMxieUsers", model);时，{p> [HttpPost]。