How to extend .NET Core IFormFileCollection

I'm developing an ASP.NET Core 5 Web API project, I want to save a post which contains multiple files. Each file should includes name and title.

Here is my code:

public class PostDTO
{
    public Guid? CategoryId { get; set; }
    public Guid UserID { get; set; }
    public string PostTitle { get; set; }
    public string PostContent { get; set; }
    public string Tags { get; set; }

    public IFormFileCollection FileList { get; set; }
}

[HttpPost]
public async Task<IActionResult> Post([FromForm] PostDTO postDTO)
{
    if (postDTO == null)
        throw new ArgumentNullException(nameof(postDTO));

    List<PostAttachmentFileDataStructure> FileList = new();

    if (postDTO.FileList != null)
        foreach (var Attachment in postDTO.FileList)
            FileList.Add(PostAttachmentFileDataStructure.Create(Guid.NewGuid(), "FileTitle", Attachment));

        try
        {
            await commandBus.Send(PostCommand.Create(Guid.NewGuid(), postDTO.PostTitle, postDTO.PostContent, postDTO.CategoryId, postDTO.UserID, postDTO.Tags.NormalizedInput(), FileList));
        }
        catch (Exception)
        {
            return StatusCode(500);
        }

        return Ok();
}

As you know IFormFile and IFormFileCollection don't have any properties like Title. So I want to extend IFormFileCollection to add another property called Title.

Is there any way to do that?

In backend:

Instead of

public class PostDTO
{
    public Guid? CategoryId { get; set; }
    public Guid UserID { get; set; }
    public string PostTitle { get; set; }
    public string PostContent { get; set; }
    public string Tags { get; set; }

    public IFormFileCollection FileList { get; set; }
}

and

public async Task<IActionResult> Post([FromForm] PostDTO postDTO){...}

you should use:

public class PostDTO
{
    public Guid? CategoryId { get; set; }
    public Guid UserID { get; set; }
    public string PostTitle { get; set; }
    public string PostContent { get; set; }
    public string Tags { get; set; }
    public List<FileInfo> FileInfos { get; set; }
}

 public class FileInfo
    {
        public string title{ get; set; }
        public string filename { get; set; }
    }

and

public async Task<IActionResult> Post( IFormCollection dto){...}

then in body you can convert data to your dto

PostDTO postDTO = JsonConvert.DeserializeObject<PostDTO>(dto["data"]);

for access to uploaded files you can use

dto.Files

In frontend:

    const data = {
            categoryId: "1",
            postTitle: "1",
            postContent: "1",
            userId: "1",
            tags: "1",
            fileInfos: [
              { title: "1", fileName: "1" },
              { title: "2", fileName: "2" },
            ],
          };
          const formData = new FormData();
          formData.append("data", JSON.stringify(data));
          formData.append("files", "file that has been uploaded");

      axios
        .post("your api URL", formData)