Error using TryUpdateModelAsync in a form with navigation properties

Question

Suppose I have a form that contains the following model structure:

TestRecord.cs

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

Where the corresponding RtdbFile contains the following props:

RtdbFile.cs

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

When I POST this model to my controller to update, I receive the following error:

The instance of entity type 'RtdbFile' cannot be tracked because another instance with the key value '{Id: 2021}' is already being tracked

So it appears that two of the same RtdbFile are being attached to the context. Here's how my controller method is formatted:

[HttpPost("UpdateMilestones")]
public async Task 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 });
}

Is TryUpdateModelAsync() not made to handle situations with a One-to-Many relationship? When is the duplicate RtdbFile being added to the context? I've disabled lazy loading and eagerly load the RtdbFiles. This is similar to what is done in the Contoso University example by Microsoft but the difference is their eagerly loaded property is a One-to-One relationship.

How can I fix this? Thanks!

EDIT to show Razor Pages:

UpdateMilestones.cshtml

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



Milestones & Tracking

The RtdbFiles are abstracted out a bit in to view components:

File View Component

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


    @(Model.AttachmentType.ToString("G"))
    
        
            @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())
                {
                    
                        @using (Html.BeginCollectionItem("RtdbFiles"))
                        {
                            
                                
                                    
                                    
                                    
                                        @if (@file.Id < 1)
                                        {
                                            
                                        }
                                        else
                                        {
                                            @file.Filename (@file.Type.ToString("G"))
                                        }
                                    
                                    
                                        
                                            Approvers:
                                            
                                        
                                    
                                
                            
                        }
                    
                }
            }
            
            
            File size limit: 100MB

Arman Ebrahimpour · Accepted Answer

What is obvious is TryUpdateModelAsync or maybe ChangeTracker has some issues with string ForeignKeys. First of all I highly recommend you to change PrimaryKey to int because EF shows some odd behaviour in such cases. But if you insist on it, I tried some ways and finally reach this way: Preventing object from tracking with AsNoTracking and use context.Update after updating record based on controller model

Based on your latest models, It's my sample that works well:

Models:

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

    public virtual IList RtdbFiles { get; set; }
}

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

Razor Page:

Note: This part has the most important effect on your result. specially RtdbFiles[{i}].Id and RtdbFiles[{i}].Filename Your View have to send items and values with exactly same name to server object to take effect correctly:

@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);
    }
    
}

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 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");
        }
    }
}

Error using TryUpdateModelAsync in a form with navigation properties

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