[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public class DisableFormValueModelBindingAttribute : Attribute, IResourceFilter
    {
        public void OnResourceExecuting(ResourceExecutingContext context)
        {
            var formValueProviderFactory = context.ValueProviderFactories
                    .OfType<FormValueProviderFactory>()
                    .FirstOrDefault();
            if (formValueProviderFactory != null)
            {
                context.ValueProviderFactories.Remove(formValueProviderFactory);
            }
            //下面这段不要忘了，对于asp.net core 6.0及以后版本，网上很多都没有这段。
            var formFileValueProviderFactory = context.ValueProviderFactories
                    .OfType<FormFileValueProviderFactory>()
                    .FirstOrDefault();
            if (formFileValueProviderFactory != null)
            {
                context.ValueProviderFactories.Remove(formFileValueProviderFactory);
            }

            var jqueryFormValueProviderFactory = context.ValueProviderFactories
                .OfType<JQueryFormValueProviderFactory>()
                .FirstOrDefault();
            if (jqueryFormValueProviderFactory != null)
            {
                context.ValueProviderFactories.Remove(jqueryFormValueProviderFactory);
            }
        }

        public void OnResourceExecuted(ResourceExecutedContext context)
        {
        }
    }

        [HttpPost("dbrestore")]
        [RequestSizeLimit(3L * 1024L * 1024L * 1024L)] //设置允许最大的文件大小为3G
        [DisableFormValueModelBinding]
        public async Task<IActionResult> UploadLargeFile([FromServices] IHttpContextAccessor httpContextAccessor)
        {
            var request = httpContextAccessor.HttpContext.Request;

            // validation of Content-Type
            // 1. first, it must be a form-data request
            // 2. a boundary should be found in the Content-Type
            if (!request.HasFormContentType ||
                !MediaTypeHeaderValue.TryParse(request.ContentType, out var mediaTypeHeader) ||
                string.IsNullOrEmpty(mediaTypeHeader.Boundary.Value))
            {
                return new UnsupportedMediaTypeResult();
            }

            var boundary = HeaderUtilities.RemoveQuotes(mediaTypeHeader.Boundary.Value).Value;
            var reader = new MultipartReader(boundary, request.Body);
            var section = await reader.ReadNextSectionAsync();

            // This sample try to get the first file from request and save it
            // Make changes according to your needs in actual use
            while (section != null)
            {
                var hasContentDispositionHeader = ContentDispositionHeaderValue.TryParse(section.ContentDisposition,
                    out var contentDisposition);

                if (hasContentDispositionHeader && contentDisposition.DispositionType.Equals("form-data") &&
                    !string.IsNullOrEmpty(contentDisposition.FileName.Value))
                {
                    // Don't trust any file name, file extension, and file data from the request unless you trust them completely
                    // Otherwise, it is very likely to cause problems such as virus uploading, disk filling, etc
                    // In short, it is necessary to restrict and verify the upload
                    // Here, we just use the temporary folder and a random file name

                    // Get the temporary folder, and combine a random file name with it
                    var fileName = Path.GetRandomFileName();
                    var saveToPath = Path.Combine(Path.GetTempPath(), fileName);

                    using (var targetStream = sysio.File.Create(saveToPath))
                    {
                        await section.Body.CopyToAsync(targetStream);
                    }

                    return new OkResult();
                }

                section = await reader.ReadNextSectionAsync();
            }

            // If the code runs to this location, it means that no files have been saved
            return new BadRequestObjectResult("No files data in the request.");
        }

参考：

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/mvc/models/file-uploads/samples/5.x/LargeFilesSample/Controllers/FileUploadController.cs

https://stackoverflow.com/questions/62502286/uploading-and-downloading-large-files-in-asp-net-core-3-1