JSON null response REST API from Biztalk Server

Calling a a REST API from Biztalk is a straightforward operation with WCF-Webhttp adapter. but when we are facing a scenario where the API is returnin an unexpeted response essentially from non maintained application. To deal with this cenario we have 2 options:

-Create a custom component piepline

-Custom behavior with message inspector

in my case,  the API return a message body containing « null » string with a 200 http status. I choose to create a custom behavior to handle the message too early on the adapter level.

My custom behavior project contains:

-a message inspector implementing IClientMessageInspector interface

the AfterReceiveReply method is fired when the response is returned from the API :

public void AfterReceiveReply(ref Message reply, object correlationState)
var replyMsg = reply.ToString();
var mystr = replyMsg.Substring(replyMsg.IndexOf(‘>’) + 1, 8);
byte[] data = Convert.FromBase64String(mystr);
string decodedString = Encoding.UTF8.GetString(data);

if (decodedString == « null »)

string response = «  »;
Message newReply = Message.CreateMessage(MessageVersion.None, null, new TextBodyWriter(response));
// very important – forces WCF to serialize the message body contents as
// « Raw » which effectively means no serialization
newReply.Properties[WebBodyFormatMessageProperty.Name] = new WebBodyFormatMessageProperty(WebContentFormat.Raw);
var responseProperty = new HttpResponseMessageProperty();
responseProperty.Headers[« Content-Type »] = « text/plain »;
newReply.Properties[HttpResponseMessageProperty.Name] = responseProperty;

reply = newReply;

catch { }

the response is received  in 64 base format : <Binary>xxxxxxxxx</Binary> »

after a converting the content and if the message is « null », with a custom writer I create a new empty message. But why an empty one?  To take benefit of the new JSON decoder « AddMessageBodyForEmptyMessag » property and to create an empty JSON message « {} »

by this way, i can avoid to receive a null reference exception.

-endpoint behavior implementing IEndpointBehavior interface

After build and GAC the dll, we have to configure this new extension:

1-C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config and C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config.


2-JSON receive pipeline conf:


3-add the extension on the send port behavior section



You can find the source code here.

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About hichamveo

I am a Microsoft certified solution developer with more than 10 years of I.T. experience working in different industry sectors(Group Life Insurance, Retail, E-Learning, E-Commerce,Infrastructure & Urban Development ) on projects ranging from small bespoke applications to multi-million Euros enterprise solutions. I am proactive in learning new technologies and like to take the responsibilities in work as it comes. Currently focused on Microsoft Integration technologies, especially BizTalk server, .NET solutions and Windows Azure.


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