How Dynamically change URL in a WCF Custom Behavior - wcf

Question

Class is defined as follows:
public class BizTalkRESTTransmitHandler : IClientMessageInspector
I'm a method with this signature:
public object BeforeSendRequest(ref Message request, IClientChannel channel)
So I think I need to manipulate the channel object.
The reason is this is being using in BizTalk 2010 SendPort to support JSON.
I tried this so far:
if (channel.RemoteAddress.Uri.AbsoluteUri == "http://api-stage2.mypartner.com/rest/events/2/"
|| channel.RemoteAddress.Uri.AbsoluteUri == "http://api.mypartner.com/rest/events/2/")
{
//TODO - "boxout" will become a variable obtained by parsing the message
Uri newUri = new Uri(channel.RemoteAddress.Uri.AbsoluteUri + "boxout");
channel.RemoteAddress.Uri = newUri;
}
Above gives compile error: "System.ServiceModel.EndpointAddress.Uri" cannot be assigned to - it is ready only" RemoteAddress seems to be read only as well.
I have referenced these questions but they don't use channel object.
Assign a URL to Url.AbsoluteUri in ASP.NET, and
WCF change endpoint address at runtime
But they don't seem to be dealing with channel object.
Update 1: I tried the following:
//try create new channel to change URL
WebHttpBinding myBinding = new WebHttpBinding();
EndpointAddress myEndpoint = new EndpointAddress(newURL);
ChannelFactory<IClientChannel> myChannelFactory = new ChannelFactory<IClientChannel>(myBinding, myEndpoint); //Change to you WCF interface
IClientChannel myNewChannel = myChannelFactory.CreateChannel();
channel = myNewChannel; //replace the channel parm passed to us
but it gave this error:
System.InvalidOperationException: Attempted to get contract type for IClientChannel, but that type is not a ServiceContract, nor does it inherit a ServiceContract.

Answer 1

IClientMessageInspector is not the right place the manipulate the Channel, you should use IEndpointBehavior instead:
From MSDN
Implements methods that can be used to extend run-time behavior for an
endpoint in either a service or client application.
Here is a simple example:
public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
{
Uri endpointAddress = endpoint.Address.Uri;
string address = endpointAddress.ToString();
if (address == "http://api-stage2.mypartner.com/rest/events/2/"
|| address == "http://api.mypartner.com/rest/events/2/")
{
//TODO - "boxout" will become a variable obtained by parsing the message
Uri newUri = new Uri(address + "boxout");
ServiceHostBase host = endpointDispatcher.ChannelDispatcher.Host;
ChannelDispatcher newDispatcher = this.CreateChannelDispatcher(host, endpoint, newUri);
host.ChannelDispatchers.Add(newDispatcher);
}
}
Here you can read the excelent post of Carlos Figueira about IEndpointBehavior:
https://blogs.msdn.microsoft.com/carlosfigueira/2011/04/04/wcf-extensibility-iendpointbehavior/
Another alternative is to implement a simple Routing with WCF, here is link with an example:
WCF REST service url routing based on query parameters
Hope it helps.

Answer 2

Using the interface IEndpointBehavior, you'll have access to the ApplyClientBehavior method, which exposes the ServiceEndPoint instance.
Now you can change the value for the Address by defining a new EndpointAddress instance.
public class MyCustomEndpointBehavior : IEndpointBehavior
{
public void AddBindingParameters(ServiceEndpoint serviceEndpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
{
}
public void ApplyClientBehavior(ServiceEndpoint serviceEndpoint, System.ServiceModel.Dispatcher.ClientRuntime behavior)
{
serviceEndpoint.Address = new System.ServiceModel.EndpointAddress("http://mynewaddress.com");
}
public void ApplyDispatchBehavior(ServiceEndpoint serviceEndpoint, System.ServiceModel.Dispatcher.EndpointDispatcher endpointDispatcher)
{
}
public void Validate(ServiceEndpoint serviceEndpoint)
{
}
}

Answer 3

I might be a bit too late but hoe it helps a bit.
I recently had a similar objective (also related to biztalk) where I needed to change the url based on some value sent on the message.
I tried using the ApplyDispatchBehavior method but it was never called and also, I couldn't see how to access the message from here so I started looking at method BeforeSendRequest (in the Inspector class).
Here is what i came up with:
object IClientMessageInspector.BeforeSendRequest(ref Message request, IClientChannel channel)
{
var queryDictionary = HttpUtility.ParseQueryString(request.Headers.To.Query);
string parameterValue = queryDictionary[this.BehaviourConfiguration.QueryParameter];
//Only change parameter value if it exists
if (parameterValue != null)
{
MessageBuffer buffer = request.CreateBufferedCopy(Int32.MaxValue);
request = buffer.CreateMessage();
//Necessary in order to read the message without having WCF throwing and error saying
//the messas was already read
var reqAux = buffer.CreateMessage();
//For some reason the message comes in binary inside tags <Binary>MESSAGE</Binary>
using (MemoryStream ms = new MemoryStream(Convert.FromBase64String(reqAux.ToString().Replace("<Binary>", "").Replace("</Binary>", ""))))
{
ms.Position = 0;
string val = ExtractNodeValueByXPath(ms, this.BehaviourConfiguration.FieldXpath);
queryDictionary.Set(this.BehaviourConfiguration.QueryParameter, DateTime.Now.ToString("yyyyMMddHHmmssfff") + "_" +
this.BehaviourConfiguration.Message + (string.IsNullOrWhiteSpace(val) ? string.Empty : "_" + val) + ".xml");
UriBuilder ub = new UriBuilder(request.Headers.To);
ub.Query = queryDictionary.ToString();
request.Headers.To = ub.Uri;
}
}
return null;
}
So, I discovered that, messing with the request.Headers.To I could change the endpoint.
I had several problems getting the message content and most examples on the internet (showing to use the MessageBuffer.CreateNavigator or Message.GetBody< string > which was always throwing an expcetion i couldn't get around) would not give me the biztalk message but rather the soap message?... not sure but it had a node header, body and inside the body there was some base64 string which was not my biztalk message.
Also, as you can see in Convert.FromBase64String(reqAux.ToString().Replace("<Binary>", "").Replace("</Binary>", "")), I had to do this ugly replaces. I don't don't why this comes in base64, probably some WCF configuration?, but by doing it, I could then look for my value.
NOTE: I haven't fully tested this, but so far it as worked for my examples.
By the way, any idea on what can i switch my MemoryStream with so it becomes a more streaming solution?