juery upload

<script type="text/javascript">
    $(document).ready(function() {
        $('#upload').click(function () {
            var data = new FormData();
            var file = $('form input[type=file]')[0].files[0];
            data.append('file',file);
            $.ajax({
                url: '/api/excels/Upload',
                processData: false,
                contentType: false,
                data: data,
                type: 'POST'
            }).done(function(result) {
                alert(result);
            }).fail(function(a, b, c) {
                console.log(a, b, c);
            });
        });
    });
</script>   

public class ExcelsController : ApiController
{
    [HttpPost]
    public async Task<string> Upload()
    {
       var provider = new MultipartMemoryStreamProvider();
       await Request.Content.ReadAsMultipartAsync(provider);

       // extract file name and file contents
       Stream stream = new MemoryStream(await provider.Contents[0].ReadAsByteArrayAsync());

       //get fileName
       var filename = provider.Contents[0].Headers.ContentDisposition.FileName.Replace("\"", string.Empty);

        //Check file type 
        if (filename .EndsWith(".xls"))
        {
            excelReader = ExcelReaderFactory.CreateBinaryReader(stream);
        }

        else if (filename .EndsWith(".xlsx"))
        {
            excelReader = ExcelReaderFactory.CreateOpenXmlReader(stream);
        }
        else
        {
            return "Not Valid";
        }
        var result = excelReader.AsDataSet(new ExcelDataSetConfiguration()
        {
            ConfigureDataTable = (_) => new ExcelDataTableConfiguration()
            {
                UseHeaderRow = true
            }
        });


       return result;
    }
}