Acjb Acjb - 1 year ago 167
ASP.NET (C#) Question

File upload using Asp.Net Core Web API file is always null

I am implememting file upload using Angular 2 with ASP.NET core Web API to handle the request.

My html code looks like :

<input #fileInput type="file"/>
<button (click)="addFile()">Add</button>

and the angular2 code

addFile(): void {
let fi = this.fileInput.nativeElement;
if (fi.files && fi.files[0]) {
let fileToUpload = fi.files[0];
.subscribe(res => {

and the service looks like

public uploadFile(file: any): Observable<any> {
let input = new FormData();
input.append("file", file,;
let headers = new Headers();
headers.append('Content-Type', 'multipart/form-data');
let options = new RequestOptions({ headers: headers });
return`/api/document/Upload`, input, options);

and the controller code

public async Task Upload(IFormFile file)
if (file == null) throw new Exception("File is null");
if (file.Length == 0) throw new Exception("File is empty");

using (Stream stream = file.OpenReadStream())
using (var binaryReader = new BinaryReader(stream))
var fileContent = binaryReader.ReadBytes((int)file.Length);
//await this.UploadFile(file.ContentDisposition);

My RequestHeader looks like

POST /shell/api/document/Upload HTTP/1.1
Host: localhost:10050
Connection: keep-alive
Content-Length: 2
Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJDb3JyZWxhdGlvbklkIjoiZDZlNzE0OTUtZTM2MS00YTkxLWExNWUtNTc5ODY5NjhjNDkxIiwiVXNlcklkIjoiMSIsIlVzZXJOYW1lIjoiWjk5OTkiLCJXb3Jrc3BhY2UiOiJRc3lzVFRAU09BVEVNUCIsIk1hbmRhbnRJZCI6IjUwMDEiLCJDb3N0Q2VudGVySWQiOiIxMDAxIiwiTGFuZ3VhZ2VDb2RlIjoiMSIsIkxhbmd1YWdlU3RyaW5nIjoiZGUtREUiLCJTdGF0aW9uSWQiOiI1NTAwMSIsIk5hbWUiOiJJQlMtU0VSVklDRSIsImlzcyI6InNlbGYiLCJhdWQiOiJodHRwOi8vd3d3LmV4YW1wbGUuY29tIiwiZXhwIjoxNDk1Mzc4Nzg4LCJuYmYiOjE0OTUzNzUxODh9.5ZP7YkEJ2GcWX9ce-kLaWJ79P4d2iCgePKLqMaCe-4A
Origin: http://localhost:10050
User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36
Content-Type: multipart/form-data
Accept: application/json, text/plain, */*
Referer: http://localhost:10050/fmea/1064001/content
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.8

The issue I am facing is that the file is always null in the controller.

Please some one help me in figuring out the issue.

Thanks in advance.

Answer Source

You don't need to use 'multipart/form-data' with FormData

In Angular 2 component:

<input type="file" class="form-control" name="documents" (change)="onFileChange($event)" />

onFileChange(event: any) {
    let fi = event.srcElement;
    if (fi.files && fi.files[0]) {
        let fileToUpload = fi.files[0];

        let formData:FormData = new FormData();
         formData.append(, fileToUpload);

        let headers = new Headers();
        headers.append('Accept', 'application/json');
        // DON'T SET THE Content-Type to multipart/form-data, You'll get the Missing content-type boundary error
        let options = new RequestOptions({ headers: headers }); + "upload/", formData, options)
                 .subscribe(r => console.log(r));

On API side

public async Task<IActionResult> Upload()
    var files = Request.Form.Files;

    foreach (var file in files)
       // to do save

    return Ok();
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