Question

would anyone have a working example of an amazon ITEMLOOKUP ?>

i have the following code but it does not seem to work:

string ISBN = "0393326381";
            string ASIN = "";

            if (!(string.IsNullOrEmpty(ISBN) && string.IsNullOrEmpty(ASIN)))
            {
                AWSECommerceServicePortTypeChannel service = new AWSECommerceServicePortTypeChannel();
                ItemLookup lookup = new ItemLookup();
                ItemLookupRequest request = new ItemLookupRequest();

                lookup.AssociateTag = secretKey;
                lookup.AWSAccessKeyId = accessKeyId;
                if (string.IsNullOrEmpty(ASIN))
                {
                    request.IdType = ItemLookupRequestIdType.ISBN;
                    request.ItemId = new string[] { ISBN.Replace("-", "") };
                }
                else
                {
                    request.IdType = ItemLookupRequestIdType.ASIN;
                    request.ItemId = new string[] { ASIN };
                }
                request.ResponseGroup = new string[] { "OfferSummary" };

                lookup.Request = new ItemLookupRequest[] { request };
                response = service.ItemLookup(lookup);

                if (response.Items.Length > 0 && response.Items[0].Item.Length > 0)
                {
                    Item item = response.Items[0].Item[0];
                    if (item.MediumImage == null)
                    {
                        //bookImageHyperlink.Visible = false;
                    }
                    else
                    {
                        //bookImageHyperlink.ImageUrl = item.MediumImage.URL;
                    }
                    //bookImageHyperlink.NavigateUrl = item.DetailPageURL;
                    //bookTitleHyperlink.Text = item.ItemAttributes.Title;
                    //bookTitleHyperlink.NavigateUrl = item.DetailPageURL;
                    if (item.OfferSummary.LowestNewPrice == null)
                    {
                        if (item.OfferSummary.LowestUsedPrice == null)
                        {
                            //priceHyperlink.Visible = false;
                        }
                        else
                        {
                            //priceHyperlink.Text = string.Format("Buy used {0}", item.OfferSummary.LowestUsedPrice.FormattedPrice);
                            //priceHyperlink.NavigateUrl = item.DetailPageURL;
                        }
                    }
                    else
                    {
                        //priceHyperlink.Text = string.Format("Buy new {0}", item.OfferSummary.LowestNewPrice.FormattedPrice);
                        //priceHyperlink.NavigateUrl = item.DetailPageURL;
                    }
                    if (item.ItemAttributes.Author != null)
                    {
                        //authorLabel.Text = string.Format("By {0}", string.Join(", ", item.ItemAttributes.Author));
                    }
                    else
                    {
                        //authorLabel.Text = string.Format("By {0}", string.Join(", ", item.ItemAttributes.Creator.Select(c => c.Value).ToArray()));
                    }
                    /*
                    ItemLink link = item.ItemLinks.Where(i => i.Description.Contains("Wishlist")).FirstOrDefault();
                    if (link == null)
                    {
                        //wishListHyperlink.Visible = false;
                    }
                    else
                    {
                        //wishListHyperlink.NavigateUrl = link.URL;
                    }
                     * */
                }
            }

        }

the problem is with this:

thisshould be defined differently but i do not know how AWSECommerceServicePortTypeChannel service = new AWSECommerceServicePortTypeChannel();

Answer 1

Say, that code looks awful familiar. You’re missing the Endpoint signing piece from when they switched over to requiring that you add message signing. You need to add a behavior on your client. Here’s the change to your code above:

if (!(string.IsNullOrEmpty(ISBN) && string.IsNullOrEmpty(ASIN)))
{
    AWSECommerceServicePortTypeClient client = new AWSECommerceServicePortTypeClient();
    client.ChannelFactory.Endpoint.Behaviors.Add(
        new Amazon.AmazonSigningEndpointBehavior(
            accessKeyId,
            secretKey);

    ItemLookup lookup = new ItemLookup();
    ItemLookupRequest request = new ItemLookupRequest();
    lookup.AssociateTag = accessKeyId;
    lookup.AWSAccessKeyId = secretKey;
//... etc.

And here’s the Endpoint (I can’t take credit for this, I wish I could remember who should):

namespace Amazon
{
    public class AmazonSigningEndpointBehavior : IEndpointBehavior {
        private string    accessKeyId    = "";
        private string    secretKey    = "";

        public AmazonSigningEndpointBehavior(string accessKeyId, string secretKey) {
            this.accessKeyId    = accessKeyId;
            this.secretKey        = secretKey;
        }

        public void ApplyClientBehavior(ServiceEndpoint serviceEndpoint, ClientRuntime clientRuntime) {
            clientRuntime.MessageInspectors.Add(new AmazonSigningMessageInspector(accessKeyId, secretKey));
        }

        public void ApplyDispatchBehavior(ServiceEndpoint serviceEndpoint, EndpointDispatcher endpointDispatcher) { return; }
        public void Validate(ServiceEndpoint serviceEndpoint) { return; }
        public void AddBindingParameters(ServiceEndpoint serviceEndpoint, BindingParameterCollection bindingParameters) { return; }
    }
}

Oh. And you’ll need the MessageInspector for that to work.

namespace Amazon
{
    public class AmazonSigningMessageInspector : IClientMessageInspector {
        private string    accessKeyId    = "";
        private string    secretKey    = "";

        public AmazonSigningMessageInspector(string accessKeyId, string secretKey) {
            this.accessKeyId    = accessKeyId;
            this.secretKey        = secretKey;
        }

        public object BeforeSendRequest(ref Message request, IClientChannel channel) {
            // prepare the data to sign
            string        operation        = Regex.Match(request.Headers.Action, "[^/]+$").ToString();
            DateTime    now                = DateTime.UtcNow;
            string        timestamp        = now.ToString("yyyy-MM-ddTHH:mm:ssZ");
            string        signMe            = operation + timestamp;
            byte[]        bytesToSign        = Encoding.UTF8.GetBytes(signMe);

            // sign the data
            byte[]        secretKeyBytes    = Encoding.UTF8.GetBytes(secretKey);
            HMAC        hmacSha256        = new HMACSHA256(secretKeyBytes);
            byte[]        hashBytes        = hmacSha256.ComputeHash(bytesToSign);
            string        signature        = Convert.ToBase64String(hashBytes);

            // add the signature information to the request headers
            request.Headers.Add(new AmazonHeader("AWSAccessKeyId", accessKeyId));
            request.Headers.Add(new AmazonHeader("Timestamp", timestamp));
            request.Headers.Add(new AmazonHeader("Signature", signature));

            return null;
        }

        public void AfterReceiveReply(ref Message reply, object correlationState) { }
    }
}

And finally, the Header:

namespace Amazon
{
    public class AmazonHeader : MessageHeader
    {
        private string name;
        private string value;

        public AmazonHeader(string name, string value)
        {
            this.name = name;
            this.value = value;
        }

        public override string Name { get { return name; } }
        public override string Namespace { get { return "http://security.amazonaws.com/doc/2007-01-01/"; } }

        protected override void OnWriteHeaderContents(XmlDictionaryWriter xmlDictionaryWriter, MessageVersion messageVersion)
        {
            xmlDictionaryWriter.WriteString(value);
        }
    }
}

Yes, they made it complicated when they started requiring message signing…