IFormFile bind error when using in sub collection

[megafetis]

Describe the bug

When i trying to post form with sublist of images models with IFormFile properties, the program starts to hang!
see the screen

To Reproduce

Steps to reproduce the behavior:

1. Using this version of ASP.NET Core '2.2'
2. Run this code

public class CategoryCreateModel
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public int Priority { get; set; }
        public string Abbr { get; set; }
        public string Description { get; set; }
        public string LinkName { get; set; }
        public string ParentId { get; set; }
// here error binding
        public IList<AppImageEditModel> Images { get; set; }
    }

//uploaded images sub collection
public class AppImageEditModel
    {
        public string Id { get; set; }
        public int Priority { get; set; }
        public string Name { get; set; }
        public string ImageUrl { get; set; }
// if class contains IFormFile prop, hapends binding bug
        public IFormFile AppImageFile { get; set; }
        public AppImageType ImageType { get; set; }
        public bool IsMain { get; set; }
    }

// in controller action:
        [HttpPost]
        public async Task<IActionResult> Create(CategoryCreateModel model)
        {
            if (ModelState.IsValid)
            {
                await Mediator.Send(model);
                return RedirectToAction("Index");
            }
            return View(model);
        }

No errors thrown, but frease executing:
operative memory encreases from 100 megabytes to 3-4 gigabytes!!!

Screenshots when I submit form:

Expected behavior

The execution is not come to action method and hangs

Binding in razor inside the form:

<form asp-action="Create" enctype="multipart/form-data">
...
<input type="text" name="Images[0].Name" id="Images_0__Text" />
<input type="file" name="Images[0].AppImageFile" id="Images_0__AppImageFile" />

<input type="text" name="Images[1].Name" id="Images_1__Text" />
<input type="file" name="Images[1].AppImageFile" id="Images_1__AppImageFile"/>

Additional context

if you delete the property public IFormFile AppImageFile from class AppImageEditModel, the program will work well!

[mkArtakMSFT]

Thanks for contacting us, @megafetis.
This is actually a dupe of aspnet/Mvc#8782, which for the fix is tracked as part of #4939

[avanveelen]

Last week I encountered the same issue, but also found a work around for it.
So, for people facing the same issue and who can not wait for a fix:

When you set the index as a hidden value in the form post, the dotnet Core model binding does not not fall into an infinite loop.
Like this:

<input type="hidden" name="Images.Index" value="0" />
<input type="text" name="Images[0].Name" />

<input type="hidden" name="Images.Index" value="1" />
<input type="text" name="Images[1].Name" />

I have made a small reproduction of the bug and included the work around.

[megafetis]

Thank you! Cool idea

[aminanan]

I would like to point out that there is no issue with previous versions of ASP.net Core. When we upgraded to ASP.NET Core '2.2' we got an OutOfMemoryException due to this issue. Now we reverted to ASP.NET Core 2.1.7 waiting for a fix.

[mkArtakMSFT]

Thanks for bringing this up, @Hakimon.
@dougbu, can you please investigate this? Thanks.

[dougbu]

This sounds like another variant of #4939 and #6616. But, it has nothing to do with [BindProperty] or [ModelBinder].

Ugly workaround would be something like

   public class CategoryCreateModel
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public int Priority { get; set; }
        public string Abbr { get; set; }
        public string Description { get; set; }
        public string LinkName { get; set; }
        public string ParentId { get; set; }

        // Following two collections should have the same number of items.
        public IList<IFormFile> Images { get; set; }
        public IList<AppImageEditModel> ImageMetadata { get; set; }
    }

    // uploaded images sub collection
    public class AppImageEditModel
    {
        public string Id { get; set; }
        public int Priority { get; set; }
        public string Name { get; set; }
        public string ImageUrl { get; set; }
        public AppImageType ImageType { get; set; }
        public bool IsMain { get; set; }
    }