downloadblob.cs

    /// <summary>
    /// Downloads a blob file.
    /// </summary>
    /// <param name="blobId">The ID of the blob.</param>
    /// <returns></returns>
    public async Task<HttpResponseMessage> GetBlobDownload(int blobId)
    {
        // IMPORTANT: This must return HttpResponseMessage instead of IHttpActionResult

        try
        {
            var result = await _service.DownloadBlob(blobId);
            if (result == null)
            {
                return new HttpResponseMessage(HttpStatusCode.NotFound);
            }

            // Reset the stream position; otherwise, download will not work
            result.BlobStream.Position = 0;

            // Create response message with blob stream as its content
            var message = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StreamContent(result.BlobStream)
            };

            // Set content headers
            message.Content.Headers.ContentLength = result.BlobLength;
            message.Content.Headers.ContentType = new MediaTypeHeaderValue(result.BlobContentType);
            message.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
            {
                FileName = HttpUtility.UrlDecode(result.BlobFileName),
                Size = result.BlobLength
            };

            return message;
        }
        catch (Exception ex)
        {
            return new HttpResponseMessage
            {
                StatusCode = HttpStatusCode.InternalServerError,
                Content = new StringContent(ex.Message)
            };
        }
    }