Question

Is there a way to synchronously process an uploaded file POSTed to a controller in the ASP.Net Web API?

I’ve tried the process Microsoft proposed here, and it works as described, but I’d like to return something other than a Task<> from the Controller method in order to match the rest of my RESTful API.

Basically, I’m wondering if there is there any way to make this work:

public MyMugshotClass PostNewMugshot(MugshotData data){
    //get the POSTed file from the mime/multipart stream <--can't figure this out
    //save the file somewhere
    //Update database with other data that was POSTed
    //return a response
}

Again, I have made the asynchronous example work but am hoping for a way to process the uploaded file before responding to the client.

Answer 1

public class UploadController : ApiController
{
    public async Task<HttpResponseMessage> Post()
    {
        if (!Request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
        }

        var appData = HostingEnvironment.MapPath("~/App_Data");
        var folder = Path.Combine(appData, Guid.NewGuid().ToString());
        Directory.CreateDirectory(folder);
        var provider = new MultipartFormDataStreamProvider(folder);
        var result = await Request.Content.ReadAsMultipartAsync(provider);
        if (result.FileData.Count < 1)
        {
            // no files were uploaded at all
            // TODO: here you could return an error message to the client if you want
        }

        // at this stage all files that were uploaded by the user will be
        // stored inside the folder we specified without us needing to do
        // any additional steps

        // we can now read some additional FormData
        string caption = result.FormData["caption"];

        // TODO: update your database with the other data that was posted

        return Request.CreateResponse(HttpStatusCode.OK, "thanks for uploading");
    }
}

You might notice that the uploaded files are stored inside the specified folder with names that might look like this: BodyPart_beddf4a5-04c9-4376-974e-4e32952426ab. That’s a deliberate choice that the Web API team made that you could override if you want.