在Blazor服务器端CRUD应用程序中进行授权，以使登录的用户查看其特定数据（不是所有用户创建的所有数据）

Question

我对这个问题感到非常难过和愚蠢，因为它对许多专家来说看起来很简单，但是这使我无休止地工作了几天，而我的解决方案却无法正常工作，这有点令人沮丧。我们将不胜感激，帮助我摆脱困境。代码链接在本文的结尾。我需要解决的是在Blazor CRUD应用程序中使用授权的方法，以便已登录的用户只能查看特定于他们的数据（由他们在登录后创建的数据）。

什么是项目？我创建了一个分配提醒列表（针对学生），其子组件“ AssignmentDetail”嵌套在名为“ AssignmentReminderList”的父组件中。子组件：具有启用输入数据的形式（作为模态），并显示分配列表：

父组件代码的重要部分：

@if (assignmentList == null)
{
    <p><em>Loading...</em></p>
}
else
{
    <table class="table">
        <thead>
            <tr>
                <th>Assignments</th>
                <th>Status</th>
                <th>Due Date</th>
                <th>Edit</th>
                <th>Delete</th>
            </tr>
        </thead>
        <tbody>
            @foreach (var assignment in assignmentList)
            {
                <tr>
                    <td>@assignment.Title</td>
                    <td>@assignment.Status</td>
                    <td>@assignment.DueDate</td>
                    <td><input type="button" class="btn btn-primary" @onclick="(()=>PrepareForEdit(assignment))" data-toggle="modal" data-target="#assignmentModal" value="Edit" /></td>
                    <td><input type="button" class="btn btn-primary" @onclick="(()=>PrepareForDelete(assignment))" data-toggle="modal" data-target="#confirmDeleteModal" value="Delete" /></td>
                </tr>
            }
        </tbody>
    </table>
}
<div>
    <input type="button" data-toggle="modal" data-target="#assignmentModal" class="btn btn-primary" value="Add Task"
           @onclick="(()=>InitializeAssignmentObject())" />
</div>
<ConfirmDelete OnClick="@Delete"></ConfirmDelete>
<AssignmentDetail AssignmentObject="assignmentObject" OnSave="@Refreshed">
    <CustomHeader>@customHeader</CustomHeader>
</AssignmentDetail>


@code {
        List<AssignmentReminder> assignmentList;
        AssignmentReminder assignmentObject = new AssignmentReminder();
        string customHeader = string.Empty;
        private readonly ApplicationDbContext _db;


        protected override async Task OnInitializedAsync()
        {
            assignmentList = await service.GetAssignments();
           await GetUserDetails();

        }

        string Message = "";
        public List<AssignmentReminder> AssignmentReminders { get; set; }



        private async Task GetUserDetails()
        {
            var authState = await AuthenticationStateProvider.GetAuthenticationStateAsync();
            var user = authState.User;

            //if (user.Identity.IsAuthenticated)
            //{
            var currentUser = await UserManager.GetUserAsync(user);

            var currentUserId = currentUser.Id;

            assignmentList = await _db.assignments.Where(a => a.OwnerID == currentUserId).ToListAsync();

        }

} 

型号是：

public class AssignmentReminder
    {

        [Key]
        public int Id { get; set; }
        //User ID from AspNetUser table
        public string OwnerID { get; set; }
        [Required(ErrorMessage = "Assignment title is required")]
        [StringLength(50, ErrorMessage = "Title is too long.")]
        public string Title { get; set; }

        [Required(ErrorMessage = "Status is required")]
        public string Status { get; set; }

        [Required(ErrorMessage = "Due Date is required")]
        public DateTime DueDate { get; set; }

    }  

现在问题是，我创建的用于过滤并获取特定于用户的数据的GetUserDetails（）方法最终在运行时Null Reference Exception中终止，因为我无法找到一种方法来填充OwnerId（在赋值中在分配表中创建记录时，该表与AspNetUser表中的userId相同。

该项目位于：https://github.com/krchome/BlazorAssignmentReminder（适用于希望在年底试用的任何人）

Answer 1

在我看来，问题在于您在创建新记录时没有保存当前用户。