c# - ASP.Net & EF Core 2 和并发 token 错误

Question

Entity Framework Core 2，向模型添加了并发 token 属性

[Timestamp]
public byte[] Timestamp { get; set; }

Controller 编辑失败

        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Edit(Guid id, [Bind("Id,Name,Description,IsDeleted,ParentId")] ItemStatus itemStatus)
        {
            if (id != itemStatus.Id)
                return NotFound();

            if (ModelState.IsValid)
            {
                try
                {
                    _context.Update(itemStatus);
                    await _context.SaveChangesAsync();
                }
                catch (DbUpdateConcurrencyException)
                {
                    if (!ItemStatusExists(itemStatus.Id))
                    {
                        return NotFound();
                    }
                    else
                    {
                        throw;
                    }
                }
                return RedirectToAction(nameof(Index));
            }

            ViewData["ParentId"] = new SelectList(_context.ItemStatus, "Id", "Description", itemStatus.ParentId);
            return View(itemStatus);
        }

发生 SaveChangesAsync 时，会出现我收到的特定错误。接住POP，当我介入时，它会直接 throw 。

DbUpdateConcurrencyException: Database operation expected to affect 1 row(s) but actually affected 0 row(s). Data may have been modified or deleted since entities were loaded. See http://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.

Microsoft.EntityFrameworkCore.Update.AffectedCountModificationCommandBatch.ThrowAggregateUpdateConcurrencyException(int commandIndex, int expectedRowsAffected, int rowsAffected)

搜索错误消息没有帮助。确实找到了这篇文章，但似乎没有帮助。

https://learn.microsoft.com/en-us/ef/core/saving/concurrency

Answer 1

如评论中所示，我缺少一个隐藏字段来“保存” View 中的时间戳。

按照这个例子:https://learn.microsoft.com/en-us/aspnet/core/data/ef-mvc/concurrency

为了清楚起见，添加了我修改过的编辑。我也必须做类似删除的事情。这需要添加到编辑 View <input type="hidden" asp-for="Timestamp" />

        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Edit(Guid id, [Bind("Id,Name,Description,ParentId,Timestamp")] ItemStatus itemStatus)
        {
            if (id != itemStatus.Id)
                return NotFound();

            if (ModelState.IsValid)
            {
                try
                {
                    _context.Update(itemStatus);
                    await _context.SaveChangesAsync();
                }
                catch (DbUpdateConcurrencyException)
                {
                    if (!ItemStatusExists(itemStatus.Id))
                    {
                        return NotFound();
                    }
                    else
                    {
                        throw;
                    }
                }
                return RedirectToAction(nameof(Index));
            }

            ViewData["ParentId"] = new SelectList(_context.ItemStatus, "Id", "Description", itemStatus.ParentId);
            return View(itemStatus);
        }