c# - 在具有导航属性的表单中使用 TryUpdateModelAsync 时出错

Question

假设我有一个包含以下模型结构的表单:

TestRecord.cs

class TestRecord {
    public string Id { get; set; }
    public string RecordName { get; set; }
    ...other props
    public ICollection<RtdbFiles> RtdbFiles { get; set; }
}

其中对应的 RtdbFile包含以下 Prop :

RtdbFile.cs

class RtdbFile {
    public int Id { get; set; }
    public string Filename { get; set; }
    ...other props
}

当我 POST这个模型到我的 Controller 更新，我收到以下错误:
The instance of entity type 'RtdbFile' cannot be tracked because another instance with the key value '{Id: 2021}' is already being tracked
所以看起来两个相同的 RtdbFile被附加到上下文中。这是我的 Controller 方法的格式:

[HttpPost("UpdateMilestones")]
public async Task<IActionResult> UpdateMilestones(string testRecordId)
{

    db.ChangeTracker.LazyLoadingEnabled = false;

    var record = db.TestRecords
        .Include(tr => tr.RtdbFiles)
        .FirstOrDefault(tr => tr.TestRecordId == testRecordId);

    if (await TryUpdateModelAsync(record))
    {
        await db.SaveChangesAsync();
    }

    return RedirectToAction("Milestones", new { id = testRecordId });
}

是 TryUpdateModelAsync()不能用 One-to-Many 处理情况关系？何时复制 RtdbFile被添加到上下文中？我已经 已禁用 延迟加载并急切加载 RtdbFiles .这与 Contoso University example by Microsoft 中所做的类似但不同之处在于他们急切加载的属性是 One-to-One关系。

我怎样才能解决这个问题？谢谢!

编辑以显示 Razor 页面:

更新里程碑.cshtml

@model rtdb.Models.TestRecord
@addTagHelper *, rtdb

<input type="hidden" asp-for="@Model.TestRecordId" />

<div class="form-section-text">Milestones & Tracking</div>

<!--unrelated inputs removed -->

<div class="form-group">
    <vc:file record="@Model" type="@RtdbFile.AttachmentType.TPR" approvers="true"></vc:file>
</div>

RtdbFiles被抽象出来以查看组件:

文件 View 组件

@model rtdb.Models.ViewModels.FileViewModel
@addTagHelper *, rtdb
@using HtmlHelpers.BeginCollectionItemCore

<div class="form-group attachments">
    <div class="link-header">@(Model.AttachmentType.ToString("G"))</div>
    <div class="row">
        <div class="col-sm-12">
            @if (Model.TestRecord.RtdbFiles.Count > 0)
            {
                foreach (var file in Model.TestRecord.RtdbFiles.Where(f => f.IsDeleted != true && f.Type == Model.AttachmentType && f.TestRecordId == Model.TestRecord.TestRecordId).ToList())
                {
                    <div class="attachment">
                        @using (Html.BeginCollectionItem("RtdbFiles"))
                        {
                            <div class="form-group">
                                <div class="form-row">
                                    <input asp-for="@file.Id" hidden />
                                    <input asp-for="@file.Type" hidden />
                                    <div class="col-sm-6">
                                        @if (@file.Id < 1)
                                        {
                                            <input class="FileInput" asp-for="@file.UploadedFile" type="file" />
                                        }
                                        else
                                        {
                                            <div><span data-file-id="@file.Id"><a href='@Url.Action("Download", "RtdbFiles", new { id = file.Id })'>@file.Filename (@file.Type.ToString("G"))</a></span></div>
                                        }
                                    </div>
                                    <div class="col-sm-6">
                                        <div>
                                            <label asp-for="@file.FileApproverPersonnel" class="col-form-label col-form-label-sm">Approvers:</label>
                                            <input asp-for="@file.FileApproverPersonnel" class="form-control file-approver-personnel ldap-tags" />
                                        </div>
                                    </div>
                                </div>
                            </div>
                        }
                    </div>
                }
            }
            <div id="@(Model.AttachmentType.ToString("G"))s"></div>
            <button type="button" class="add-file btn btn-primary" data-test-type="Other" data-attachment-type="TPR" data-container="@(Model.AttachmentType.ToString("G"))s">Add @(Model.AttachmentType.ToString("G"))</button>
            <small style="display: block; margin-top: 6px">File size limit: 100MB</small>
        </div>
    </div>
</div>

Answer 1

显而易见的是TryUpdateModelAsync或者 ChangeTracker string 有一些问题外键。首先，我强烈建议您将 PrimaryKey 更改为 int因为 EF 在这种情况下会表现出一些奇怪的行为。
但是如果你坚持，我尝试了一些方法，最后达到了这个方法:
使用 AsNoTracking 阻止对象跟踪并使用 context.Update根据 Controller 模型更新记录后

根据您的最新型号，这是我的示例，效果很好:

楷模:

public class TestRecord
{
    public string Id { get; set; }
    public string RecordName { get; set; }

    public virtual IList<RtdbFile> RtdbFiles { get; set; }
}

public class RtdbFile
{
    public int Id { get; set; }
    public string TestRecordId { get; set; }
    public string Filename { get; set; }
}

Razor 页面:

备注 :这部分对你的结果有最重要的影响。特别 RtdbFiles[{i}].Id和 RtdbFiles[{i}].Filename您的 View 必须将名称完全相同的项目和值发送到服务器对象才能正确生效:

@model Jordan.TestRecord

@using (Html.BeginForm("UpdateMilestones", "Home", FormMethod.Post))
{
    @Html.HiddenFor(p => p.Id);

    @for (int i = 0; i < Model.RtdbFiles.Count; i++)
    {
        @Html.Hidden($"RtdbFiles[{i}].Id", Model.RtdbFiles[i].Id);
        @Html.TextBox($"RtdbFiles[{i}].Filename", Model.RtdbFiles[i].Filename);
    }
    <button type="submit">Save</button>
}

Controller :

namespace Jordan
{
    [Route("")]
    public class HomeController : Controller
    {
        private readonly AppDbContext context;

        public HomeController(AppDbContext context)
        {
            this.context = context;
            context.Database.EnsureCreated();
        }

        [HttpGet]
        public IActionResult Index()
        {
            var sampleRecord = context.TestRecords
                .Include(r => r.RtdbFiles)
                .FirstOrDefault();

            return View(sampleRecord);
        }

        [HttpPost]
        [Route("UpdateMilestones")]
        public async Task<IActionResult> UpdateMilestones(int Id)
        {
            context.ChangeTracker.LazyLoadingEnabled = false;

            var record = context.TestRecords
                .Include(tr => tr.RtdbFiles)
                .AsNoTracking()
                .FirstOrDefault(tr => tr.Id == Id);

            if (await TryUpdateModelAsync(record))
            {
                context.Update(record);
                await context.SaveChangesAsync();
            }

            return RedirectToAction("Index");
        }
    }
}