Multiple form-data file upload parameters

Question

I'd like to use the ng2-file-upload component on the client side and everything works so far but now I have to pass an additional parameter with every file that contains an identifier the file is attached to. I try to set the additionalParameter property of the FileUploader object in TypeScript:

this.uploader.options.additionalParameter = {"issueId": result.data.id};

On the server I have the following method that is working except I don't get the additional parameter (issueId) set above. (.NET Core 2.0)

public RequestResultModel File(IFormFile file);

The request payload contains the parameter but in a new form-data:

------WebKitFormBoundaryegtYAcYfO3gKdk9Z
Content-Disposition: form-data; name="file"; filename="81980085.pdf"
Content-Type: application/pdf


------WebKitFormBoundaryegtYAcYfO3gKdk9Z
Content-Disposition: form-data; name="issueId"

19
------WebKitFormBoundaryegtYAcYfO3gKdk9Z-- 

How can I modify the controller method in order to read the issueId parameter as well? In a previous project I used a second parameter public async Task<ApiResultBase> Upload(IFormFile file, string projectid) and it worked but now I would like to use this client side component because I don't want to suck with drag and drop and I'm lazy. I have tried to change the component's POST url after initialize (this.uploader.options.url = "/api/Issue/File/"+result.data.id;) but it tries to POST to the original address.

Answer 1

You are on track. I have a slightly different approach you can try out.On the client, try something like:

this.uploader = new FileUploader({
            url: url,//The enpoint you are consuming
            additionalParameter: {
                issueId: result.data.id //your parameter-remove quotes
            },
            headers: [{ name: 'Accept', value: 'application/json' }],//your custom header
            //autoUpload: true, //configure autoUpload
        });

The library also has onErrorItem and onSuccessItem callbacks that you can leverage like below:

this.uploader.onErrorItem = (item, response, status, headers) => this.onErrorItem(item, response, status, headers);
this.uploader.onSuccessItem = (item, response, status, headers) => this.onSuccessItem(item, response, status, headers);

Then(Optional) - Callbacks:

    onSuccessItem(item: FileItem, response: string, status: number, headers:ParsedResponseHeaders): any {
            //this gets triggered only once when first file is uploaded       
     }
    onErrorItem(item: FileItem, response: string, status: number, headers: 
           ParsedResponseHeaders): any {
                let error = JSON.parse(response); //error server response            
            }

On the API side you can restructure like below - Change it to your own signature.

 public async Task<IActionResult> UploadImages(MyFile upload)

Then the MyFile model can be something like:

public class MyFile
    {
        public string issueId { get; set; }        
        public IFormFile File { get; set; }
    }

To get the param and the file:

var file = upload.File //This is the IFormFile file
var param = upload.issueId //param

To save the file to disk:

using (var stream = new FileStream(path, FileMode.Create))
        {
            await file.File.CopyToAsync(stream);
        }