Upload a file using Angular 6 to Web Api C#

At angular site use this code

file: any;

onSelectFile($event, file) {
    this.file = file;
  }


  uploadImage() {
    if (this.file.length === 0) {
      return;
    }

    const formData = new FormData();

    for (let file of this.file)
      formData.append(file.name, file);

    const uploadReq = new HttpRequest('POST', `api/FileUpload`, formData, {
      reportProgress: true,
    });

    this.http.request(uploadReq).subscribe(event => {
      if (event.type === HttpEventType.UploadProgress) {
        this.progress = Math.round(100 * event.loaded / event.total);
      }
    });
  }

here onSelectFile should be called on input like this

<input #file type='file' multiple (change)="onSelectFile($event, file.files)">

And at your asp.net site use this code

[Produces("application/json")]
    [Route("api/[controller]")]
    public class FileUploadController : Controller
    {
    private IHostingEnvironment _hostingEnvironment;

    public FileUploadController(IHostingEnvironment hostingEnvironment)
    {
      _hostingEnvironment = hostingEnvironment;
    }

    [HttpPost, DisableRequestSizeLimit]
    public ObjectResult UploadFile()
    {
      try
      {
        var file = Request.Form.Files[0];
        string folderName = "Upload";
        string webRootPath = _hostingEnvironment.WebRootPath;
        string newPath = Path.Combine(webRootPath, folderName);
        if (!Directory.Exists(newPath))
        {
          Directory.CreateDirectory(newPath);
        }
        string fileName = "";
        if (file.Length > 0)
        {
          fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');
          string fullPath = Path.Combine(newPath, fileName);
          using (var stream = new FileStream(fullPath, FileMode.Create))
          {
            file.CopyTo(stream);
          }
        }

        return Ok(fileName);
      }
      catch (System.Exception ex)
      {
        return BadRequest(ex.Message);
      }
    }
  }

Thanks

https://github.com/BhadraAnirban/angular_file_upload_net_core

The process is to send the base64 string from Angular using POST call in the FormBody and at .net core convert the string to byte.

Note - FormData will not work in AWS Lambda properly, it will corrupt the file. So this is a better approach to send mail or upload file in AWS as well.

HTML -

<form class="row">
    <input id="{{id}}" type="file" (change)="FileSelected($event.target.files);">
</form>
<div id="hidden_upload_item" style="display: none;"></div>

Typescript -

FileSelected(files){
    this.fileData = <File>files[0];
    this.FileName = this.fileData.name;
    let reader = new FileReader();
    var selectedFile = <File>files[0];

    reader.onload = function (readerEvt: any) {
        var arrayBuffer = readerEvt.target.result.toString().split('base64,')[1];     
        document.querySelector('#hidden_upload_item').innerHTML = arrayBuffer;
        this.Proceed();
    }.bind(this);
    reader.readAsDataURL(selectedFile);

  }

  Proceed()
  {
    var item = document.querySelector('#hidden_upload_item').innerHTML;
    let formdata = new UploadFile();
    formdata.data = item;
    formdata.name = this.FileName;
    this.UploadDocument(formdata)
      .subscribe(event => {
        // Perform other operations
      }, err => {
        this.InProgress = false;
      });
  }

  UploadDocument(formData){
        const httpOptions = {
          headers: new HttpHeaders({
            'Content-Type': 'application/json'
          })
        };
        return this.http.post('/api/document/uploaddocument', formData, httpOptions);
      } 

.net Core -

[HttpPost("uploaddocument"), DisableRequestSizeLimit]
public IActionResult UploadDocument([FromBody] FileModel fileModel)
        {
            try
            {
                    var value = fileModel.Data;
                    var byteArray = Convert.FromBase64String(value);
                    var fileExtension = Path.GetExtension(fileModel.Name);
                    var fileName = fileModel.Name;

                    /// Now save in Database or AWS

                }
                return Ok();
            }
            catch (Exception e)
            {
                throw e;
            }

        }        

 public class FileModel
{
    public string Data { get; set; }
    public string Name { get; set; }
}

I had used the solution of @Elon Musk but Request.Form.Files[0]gives me the Evaluation timeout exception, so to handle it, I have added the Iformfile parameter in Actionmethod in .net side

public IActionResult UploadFile(IFormFile formfile)