亚马逊产品广告API ItemSearch返回空值

Question

I have spent entire day trying to fix problems with the Amazon ECS(Ecommerce Services) API.

I have downloaded the example on their site for sending SOAP Requests with .NET 4.0 and WCF

http://aws.amazon.com/code/Product-Advertising-API/3941

I have not changed anything in the code from the example, except for the AccessKeyID and SecretyKeyID in the config file.

The Calling code looks like the following:

        // Instantiate Amazon ProductAdvertisingAPI client
        AWSECommerceServicePortTypeClient amazonClient = new AWSECommerceServicePortTypeClient();

        // prepare an ItemSearch request
        ItemSearchRequest request = new ItemSearchRequest();
        request.SearchIndex = "Books";
        request.Title = "WCF";
        request.ResponseGroup = new string[] { "Medium"};

        ItemSearch itemSearch = new ItemSearch();
        itemSearch.Request = new ItemSearchRequest[] { request };
        request.Condition = Condition.All;
        itemSearch.AssociateTag = "";
        itemSearch.AWSAccessKeyId = ConfigurationManager.AppSettings["accessKeyId"];

        // send the ItemSearch request
        ItemSearchResponse response = amazonClient.ItemSearch(itemSearch);
        if (response != null)
        {
            // write out the results from the ItemSearch request
            foreach (var item in response.Items[0].Item)
            {
                Console.WriteLine(item.ItemAttributes.Title);
            }
        }
        Console.WriteLine("done...enter any key to continue>");
        Console.ReadLine();

the Call to the ItemSearch() is returning a null object. I looked further into this and saw that in the AmazongSigningMessageInspector Class, the AfterReceiveReply() method is showing that a proper SOAP XML response is being returned with results, so I know that it is making the call to the service and returning correctly. For some reason though I am left with a NULL ItemSearch object.

The code for my classes are the following:

class AmazonSigningBehaviorExtensionElement : BehaviorExtensionElement
{
    public AmazonSigningBehaviorExtensionElement()
    {
    }

    public override Type BehaviorType
    {
        get
        {
            return typeof(AmazonSigningEndpointBehavior);
        }
    }

    protected override object CreateBehavior()
    {
        return new AmazonSigningEndpointBehavior(AccessKeyId, SecretKey);
    }

    [ConfigurationProperty("accessKeyId", IsRequired = true)]
    public string AccessKeyId
    {
        get { return (string)base["accessKeyId"]; }
        set { base["accessKeyId"] = value; }
    }

    [ConfigurationProperty("secretKey", IsRequired = true)]
    public string SecretKey
    {
        get { return (string)base["secretKey"]; }
        set { base["secretKey"] = value; }
    }
}


public class AmazonSigningEndpointBehavior : IEndpointBehavior {
    private string  _accessKeyId    = "";
    private string  _secretKey  = "";

    public AmazonSigningEndpointBehavior()
    {
        this._accessKeyId = ConfigurationManager.AppSettings["accessKeyId"];
        this._secretKey = ConfigurationManager.AppSettings["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; }
}

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)
    {


    }
}

I have seen this problem everywhere, but nobody has posted a fix for it anywhere. Somebody please help me with this.

Answer 1

My issue was that I was missing the associate tag.

itemSearch.AssociateTag = "213";

There are definitely problems with the generated code, ItemSearchResponse contains an error collection which is not exposed by code. It was through looking at the raw message in the inspector that pointed me in the right direction.

Answer 2

The answer regarding missing associate tag help me, but I also had to ensure the WSDL URL and endpoint address match the Amazon site you've registered under. I registered under the UK site so I need to use.

WSDL
Endpoint Address

Answer 3

A current project to this assignment you can found here on Nager.AmazonProductAdvertising github. The library is also available over nuget

nuget

PM> Install-Package Nager.AmazonProductAdvertising

Example

var authentication = new AmazonAuthentication();
authentication.AccessKey = "accesskey";
authentication.SecretKey = "secretkey";

var wrapper = new AmazonWrapper(authentication, AmazonEndpoint.US);
var result = wrapper.Search("canon eos", AmazonSearchIndex.Electronics, AmazonResponseGroup.Large);

Answer 4

I compiled and posted a fix for this sample. Please go here: https://forums.aws.amazon.com/message.jspa?messageID=440527#440527