有时上传的文件在 C# Angular 8 中为空

Question

我的应用程序允许我在表单中上传文档文件（必填字段）。 在数据库中，我们有存储上传文件路径的“文档”列。 有时，对于某些用户，用户正在填写表单，当他们单击保存按钮时数据已成功插入，但“文档”列中的 null 值，上传文件路径中也没有上传文件。 从前端，我正在验证（必填字段）文档上传字段，但 null 值仍将进入数据库，也不会在日志文件中引发任何异常。

有什么办法可以捕捉到这方面的异常吗？

'提交控制器.cs'

[HttpPost]
        [Route("Add")]
        public string AddRecord([FromBody]ProductionUpload data)
        {
            string recaptcha = string.Empty;

            try
            {
                'Validate the model'
                if (!ModelState.IsValid)
                {
                    throw new Exception("Server-side validation message(s): " +
                                        ModelState.Values.Select(v => v.Errors.Select(e => e.ErrorMessage).Aggregate((a, b) => a + "; " + b))
                                                         .Aggregate((a, b) => a + "; " + b));
                }

                'Validate Recaptcha response'
                if (!ValidateRecaptchaResponse(data.Recaptcha))
                {
                    throw new Exception("Invalid Recaptcha response: " + data.Recaptcha);
                }

                'Save the request to DB'
                data.DateOfSubmission = DateTime.UtcNow;
                _context.ProductionUploads.Add(data);
                _context.SaveChanges();

                data.RegistryNumber = "P" + data.Id.ToString().PadLeft(6, '0');
                _context.SaveChanges();

                recaptcha = data.Recaptcha;
            }
            catch (Exception ex)
            {
                SendExceptionEmail(ex);
                _logger.LogError("{0}\n{1}", ex.Message, ex.StackTrace);
                throw;
            }

            return recaptcha;
        }

        [HttpPost]
        [DisableRequestSizeLimit]
        [Route("Upload")]
        public void UploadDocument()
        {
            List<ProductionUpload> fileData = new List<ProductionUpload>();

            try
            {
                var recaptcha = Request.Form["data"].ToString();
                var files = Request.Form.Files;

                // Validate the document
                if (files.Count > 0)
                {
                    uint maximumDocumentSize = _configuration.GetSection("AppSettings").GetValue<uint>("MaximumDocumentSize");
                    List<FileType> allowedDocumentTypes = _configuration.GetSection("AppSettings:AllowedDocumentTypes").Get<List<FileType>>();

                    var fileExt = Path.GetExtension(files[0].FileName);
                    if (files[0].Length == 0 || files[0].Length > maximumDocumentSize ||
                        (!allowedDocumentTypes.Any(ft => ft.Extension.ToLower() == fileExt.ToLower() && (string.IsNullOrEmpty(ft.ContentType) || ft.ContentType.ToLower() == files[0].ContentType.ToLower()))))
                    {
                        throw new Exception(string.Format("Server-side file validation failure: {0}, {1} bytes, {2} content type", files[0].FileName, files[0].Length, files[0].ContentType));
                    }
                }

                'Validate the cover letter
                if (files.Count > 1)
                {
                    uint maximumCoverLetterSize = _configuration.GetSection("AppSettings").GetValue<uint>("MaximumCoverLetterSize");
                    List<FileType> allowedCoverLetterTypes = _configuration.GetSection("AppSettings:AllowedCoverLetterTypes").Get<List<FileType>>();

                    var fileExt = Path.GetExtension(files[1].FileName);
                    if (files[1].Length == 0 || files[1].Length > maximumCoverLetterSize ||
                        (!allowedCoverLetterTypes.Any(ft => ft.Extension.ToLower() == fileExt.ToLower() && (string.IsNullOrEmpty(ft.ContentType) || ft.ContentType.ToLower() == files[1].ContentType.ToLower()))))
                    {
                        throw new Exception(string.Format("Server-side file validation failure: {0}, {1} bytes, {2} content type", files[1].FileName, files[1].Length, files[1].ContentType));
                    }
                }

                'Get the previously saved Submission from the database'
                ProductionUpload productionUpload = _context.ProductionUploads.SingleOrDefault(sr => sr.Recaptcha == recaptcha);
                if (productionUpload == null || productionUpload.Id == 0)
                {
                    throw new Exception("Invalid Recaptcha response: " + recaptcha);
                }

                'Save the uploaded files'
                string fileUploadPath = _configuration.GetSection("AppSettings").GetValue<string>("FileUploadPath");
                string pathToSave = Path.Combine(fileUploadPath, Guid.NewGuid().ToString());

                if (!Directory.Exists(pathToSave))
                    Directory.CreateDirectory(pathToSave);

                for (int i = 0; i < files.Count; i++)
                {
                    var fileName = Path.GetFileName(files[i].FileName);
                    var localFileName = ReplaceInvalidCharacters(fileName);

                    var dbPath = Path.Combine(pathToSave, localFileName);
                    using (var stream = new FileStream(dbPath, FileMode.Create))
                    {
                        files[i].CopyTo(stream);
                    }

                    if (i == 0)
                    {
                        productionUpload.Documents = dbPath;
                    }
                    else
                    {
                        productionUpload.CoverLetter = dbPath;
                    }
                }

                _context.SaveChanges();
            }
            catch (Exception ex)
            {
                SendExceptionEmail(ex);
                _logger.LogError("{0}\n{1}", ex.Message, ex.StackTrace);
                throw;
            }
        }

'home-component.ts'

ngOnInit() {
    this.requestForm = this.formBuilder.group({
      Id: ['', ''],
      ProducingEntity: [null, Validators.required],
      PartyCode: [null,Validators.required],
      RepresentedBy: [null],
      ContactName: [null, Validators.required],
      Email: [null, [Validators.required, Validators.pattern(this.emailPattern)]],
      ContactNumber: [null, [Validators.required, Validators.pattern(this.phoneNumberPattern)]],
      ReferenceNumber: [null],
      NoticeToProduceNumber: [null, [Validators.required, Validators.pattern(this.ntpPattern)]],
      TrancheNumber: [null, Validators.pattern(this.tranchePattern)],
      ReplacementFiles: [null, Validators.required],
      UploadMaterial: [null, Validators.required],
      Password: [null],
      Description: [null],
      Recaptcha: [null, Validators.required]
    });
    this.requestForm.controls.Id.setValue(0);
  }

HandleDocumentInput(files: FileList) {
    if (files != null && files.length > 0) {
      this.ShowDocumentAlertMessage = false;
      if (!this.ValidateFileSize(files.item(0), this.maxDocumentSize)) {
        this.documentUploader.queue.pop();
        this.DocumentAlertMessageType = 2; // failure
        this.DocumentMessage = "File size must be greater than 0 and cannot exceed 4GB.";
        this.ShowDocumentAlertMessage = true;
        this.documentInput.nativeElement.value = '';
        return;
      }
      if (!this.ValidateFileType(files.item(0), this.allowedDocumentExtensions)) {
        this.documentUploader.queue.pop();
        this.DocumentAlertMessageType = 2; // failure
        this.DocumentMessage = "Files with this extension cannot be uploaded.";
        this.ShowDocumentAlertMessage = true;
        this.documentInput.nativeElement.value = '';
        return;
      }
      this.DocumentFile = files.item(0);
      this.DocumentName = files.item(0).name;
      this.IsDocumentUploaded = true;
      this.documentInput.nativeElement.value = '';
    }
  }

'app-service.ts'

Submit(productionUpload: ProductionUpload) {
    const apiUrl = window.location.href + 'ProductionUpload/Add';
    const httpOptions = {
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
      }),
      responseType: 'text' as 'json'
    };
    productionUpload.ReplacementFiles = +productionUpload.ReplacementFiles;
    productionUpload.IsDeleted = false;
    productionUpload.IsProcessed = false;
    return this._http.post<string>(apiUrl, productionUpload, httpOptions);
  }

  UploadFile(recaptcha, fileToUpload: File[]) {
    const apiUrl = window.location.href + 'ProductionUpload/Upload';
    const formData: FormData = new FormData();

    if (fileToUpload && fileToUpload.length) 
    {
       fileToUpload.forEach(file => formData.append('files', file));
    }
    formData.append('data', recaptcha)
    return this._http.post(apiUrl, formData);
  }

'Exception getting' 客户端已断开连接

at Microsoft.AspNetCore.Server.IIS.Core.IO.AsyncIOOperation.GetResult(Int16 token) at Microsoft.AspNetCore.Server.IIS.Core.IISHttpContext.ReadBody() at System.IO.Pipelines.PipeCompletion.ThrowLatchedException() at System .IO.Pipelines.Pipe.GetReadResult(ReadResult& result) at System.IO.Pipelines.Pipe.GetReadAsyncResult() at Microsoft.AspNetCore.Server.IIS.Core.IISHttpContext.ReadAsync(Memory 1 memory, CancellationToken cancellationToken) at Microsoft.AspNetCore.Server.IIS.Core.HttpRequestStream.ReadAsyncInternal(Memory 1 缓冲区，CancellationToken cancelToken）在 Microsoft.AspNetCore.WebUtilities.BufferedReadStream.EnsureBufferedAsync（Int32 minCoun t，Microsoft.AspNetCore.WebUtilities.MultipartReaderStream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancelToken) at Microsoft.AspNetCore.WebUtilities.FileBufferingReadStream.ReadAsync(Byte[] buffer, Int32 offset, Int32 处的 CancellationToken cancelToken) count, CancellationToken cancellationToken) at Microsoft.AspNetCore.WebUtilities.StreamHelperExtensions.DrainAsync(Stream stream, ArrayPool 1 bytePool, Nullable 1 limit, CancellationToken cancellationToken) at Microsoft.AspNetCore.Http.Features.FormFeature.InnerReadFormAsync(CancellationToken cancellationToken) at Microsoft.AspNetCore .Http.Features.FormFeature.ReadForm() 在 Microsoft.AspNetCore.Http.DefaultHttpRequest.get_Form()