Question

我正在使用带有ASP.NET核心Web API的Angular 2来实现文件上传来处理请求。

我的HTML代码如下：

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

和angular2代码

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

，服务看起来像

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

和控制器代码

[HttpPost]
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);
        }
    }
}

我的RequestHeader看起来像

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

我面临的问题是控制器中的文件始终为空。

请有人帮助我解决问题。

提前致谢。

Answer 1

您不需要在FormData

中使用'multipart / form-data'

在Angular 2组件中：

<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.name, 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 });

        this.http.post(this.baseUrl + "upload/", formData, options)
                 .subscribe(r => console.log(r));
    }
}

在API方面

[HttpPost("upload")]
public async Task<IActionResult> Upload()
{
    var files = Request.Form.Files;

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

    return Ok();
}

Answer 2

更新：经过ASP.NET Core团队的澄清后，它与Startup类中的compat开关有关。如果您这样设置：

services
    .AddMvc()
    .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

那么如果您还从文件参数中删除[FromForm]属性，就可以了。

旧帖子：我遇到了与最新的ASP.NET Core WebApi（在撰写本文时为2.1.2）类似的问题，在经过一个小时的堆栈溢出，研究和大量的反复试验后，我只能偶然解决。我是从这样的Angular 6应用程序发布文件的：

const formData: FormData = new FormData();
formData.append('file', file, file.name);

const req = new HttpRequest('POST', 'upload-url', formData, {
    reportProgress: true
});

this.http.request(req).subscribe(...) // omitted the rest

问题在于，即使将IFormFile file放在前面，null动作方法参数始终是[FromForm]。由于ASP.NET Core 2.1中的api控制器行为发生了更改，因此[FromForm]是必需的，其中[FromBody]成为api控制器的默认设置。奇怪的是，它仍然不起作用，其值仍然为null。

我终于通过使用属性明确说明表单内容参数的名称来解决了这个问题，

public async Task<IActionResult> UploadLogo([FromForm(Name = "file")] IFormFile file)        
{
     ...
}

现在，文件上传已正确绑定到控制器参数。我希望这会在将来对某人有所帮助，因为这几乎使我失去理智：D

Answer 3

使用dotnet核心的另一种方法，您可以使用IFormFile接口，并设置默认标头：

Angular 2

 let formData = new FormData();
 formData.append("file", yourUploadFile);

 this.http.post("your_api_path", formData).subscribe(r => console.log(r));

Dotnet Core

 [HttpPost]
 [Route("/your_api_path")]
 public async Task<IActionResult> Upload(IFormFile file) {
     //...next awaiters...    
}

如果要发送多个文件，可以使用ICollection<IFormFile>作为上传参数。

对于发送多个属性，您可以使用自定义模型对象，IFormFile将是属性之一。

希望有所帮助！

Answer 4

Core 3.1

[HttpPost("upload-bulk-excel"), DisableRequestSizeLimit]
public IActionResult Upload()
{
  try
  {
    var file = Request.Form.Files[0];

角度8

uploadExcelFile() {
  const formData = new FormData();
  formData.append('file', this.fileToUpload, this.fileToUpload.name);

  this._httpClient.post(`${environment.apiUrl}/upload/upload-bulk-excel`, formData, {reportProgress: true, observe: 'events'})
    .subscribe(event => {
      if (event.type === HttpEventType.UploadProgress)
        this.uploadProgress = Math.round(100 * event.loaded / event.total);
      else if (event.type === HttpEventType.Response) {
        this.uploadMessage = 'Upload success.';
      alert('File uploaded successfully');
    }
  });

}

使用Asp.Net Core Web API文件上传文件始终为null

4 个答案: