How can I fix 415 unsupported media type on file upload in Angular 6

Question

I work on a .Net Core Web Api and an Angular application. I created a controller which links an image to an item in database:

[HttpPut("[Action]/{id}")]
public async Task<ActionResult<Item>> LinkItemToIcon(int id, IFormFile file)
{
    var items = await _context.Items.FirstOrDefaultAsync(t => t.Id == id);

    if (items == null)
    {
        return BadRequest("item null");
    }

    if (file.Length <= 0)
    {
        return BadRequest("fileEmpty");
    }

    using (var memoryStream = new MemoryStream())
    {
        await file.CopyToAsync(memoryStream);
        Item item = new Item() { Id = items.Id, Icon = memoryStream.ToArray() };
        _context.Entry(items).CurrentValues.SetValues(item);
        _context.SaveChanges();

        return Ok(file);
    }
}

It works well in Postman, but when I want to use the controller, I get an error:

Headers: HttpHeaders {normalizedNames: Map(0), lazyUpdate: null, headers: Map(0)} message: "Http failure response for https://localhost:5001/api/LinkItemToIcon: 415 Unsupported Media Type"
name: "HttpErrorResponse"
ok: false
status: 415
statusText: "Unsupported Media Type"
url: "https://localhost:5001/api/LinkItemToIcon"

You can see my html in my angular application :

<input type="file" (change)="onSelectedFile($event) name="file">
<input type="button" (click)="linkItem()">

You can see my component :

this.selectedFile : File = null ;
onSelectedFile(e){
    this.selectedFile = e.target.files[0]
}
LinkItem(){
    var formData = new FormData();
    formData.append("file",this.selectedFile, this.selectedFile.name)
    this.administrator.LinkItemToIcon(1,formData).subscribe(
       r => console.log(r),
       err => console.log(err)
    )
}

And now my service:

  LinkItemToIcon(id,file){
return this.http.put<UploadFile>(`${this.config.catchApiUrl()}Item/LinkItemToIcon/`+ id, file
,{
  headers : new HttpHeaders({
    'Content-Type' : 'application/json'
  })}
)

}

My breakpoint result :

Think you for your help. breakpoint result

And I have an error message when I want to subscribe to linkItemToIcon

FormData is not defined

Moreover I can change in my code my content-type which is application/json to multipart/form-data because I have an

PUT https://localhost:5001/api/Item/LinkItemToIcon/1 500 (Internal Server Error)

Access to XMLHttpRequest at 'https://localhost:5001/api/Item/LinkItemToIcon/1' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

HttpErrorResponse {headers: HttpHeaders, status: 0, statusText: "Unknown Error", url: null, ok: false, …}

Solution 1

Follow steps below for a working demo:

1. Controller

   [HttpPut("[Action]/{id}")]
   public async Task<ActionResult> LinkItemToIcon(int id, IFormFile file)
   {
       //your operation
   }
   

2. Angular

   selectedFile : File = null;
   onSelectedFile(e){
       this.selectedFile = e.target.files[0];
   }
   linkItem(){
       var formData = new FormData();
       formData.append("file", this.selectedFile, this.selectedFile.name)
       this.LinkItemToIcon(1, formData).subscribe(
       r => console.log(r),
       err => console.log(err)
       )
   }
   LinkItemToIcon(id, formData) {
       return this.http.put(`api/SampleData/LinkItemToIcon/` + id, formData);
   }
   

Solution 2

Do you have to send it through javascript/Angular? There's a much less convoluted way to send it straight from the form:

<form id="yourid" action=".../yourpath/LinkItemToIcon" method="PUT" enctype="multipart/form-data">
 <input type="file" name="file"/>
 <input type="hidden" name="id" value="yourID"/>
 <button type="submit">
  <span>Submit</span>
 </button>
</form>

And if you have trouble with the id being passed you can just pass that via Attribute Routing

Comments

[CryptoChrisJames]

What happened? Was it the same error? What kind of file is it and what is the size?

[CryptoChrisJames]

Okay, I just noticed that you are already using attribute routing for your action, so you can actually leave out that hidden field and change the method to method=".../yourpath/LinkItemToIcon/yourid". Did you try that?