Я использовал следующий код для загрузки файла на сервер, но файл не загружен.

Html:

      
        
            
            
                
            
        
        Upload
    

Javascript:

     // Hook into the form's submit event.
    $('#upload').submit(function () {

        // To keep things simple in this example, we'll
        // use the FormData XMLHttpRequest Level 2 object (which
        // requires modern browsers e.g. IE10+, Firefox 4+, Chrome 7+, Opera 12+ etc).
        var formData = new FormData();

        // We'll grab our file upload form element (there's only one, hence [0]).
        var opmlFile = $('#opmlFile')[0];

        // If this example we'll just grab the one file (and hope there's at least one).
        formData.append("opmlFile", opmlFile.files[0]);

        // Now we can send our upload!
        $.ajax({
            url: 'api/upload', // We'll send to our Web API UploadController
            data: formData, // Pass through our fancy form data

            // To prevent jQuery from trying to do clever things with our post which
            // will break our upload, we'll set the following to false
            cache: false,
            contentType: false,
            processData: false,

            // We're doing a post, obviously.
            type: 'POST',

            success: function () {
                // Success!
                alert('Woot!');
            }
        });

        // Returning false will prevent the event from
        // bubbling and re-posting the form (synchronously).
        return false;
    });

контроллер как следует:

         using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Web;
using System.Web.Http;

class UploadController : ApiController
{
    public async void Post()
    {
        if (!Request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotAcceptable, "This request is not properly formatted"));
        }

        // We'll store the uploaded files in an Uploads folder under the web app's App_Data special folder
        var streamProvider = new MultipartFormDataStreamProvider(HttpContext.Current.Server.MapPath("~/App_Data/Uploads/"));

        // Once the files have been written out, we can then process them.
        await Request.Content.ReadAsMultipartAsync(streamProvider).ContinueWith(t =>
        {
            if (t.IsFaulted || t.IsCanceled)
            {
                throw new HttpResponseException(HttpStatusCode.InternalServerError);
            }

            // Here we can iterate over each file that got uploaded.
            foreach (var fileData in t.Result.FileData)
            {
                // Some good things to do are to check the MIME type before we do the processing, e.g. for XML:
                if (fileData.Headers.ContentType.MediaType.Equals("text/xml", StringComparison.InvariantCultureIgnoreCase))
                {
                    // And this is how we can read the contents (note you would probably want to do this asychronously
                    // but let's try keep things simple for now).
                    string contents = File.ReadAllText(fileData.LocalFileName);
                }
            }
        });
    }
}

Действие выполнено, но файл не загружен.