How to add a custom HTTP header to every WCF call?

Question

I have a WCF service that is hosted in a Windows Service. Clients that using this service must pass an identifier every time they're calling service methods (because that identifier is important for what the called method should do). I thought it is a good idea to somehow put this identifier to the WCF header information.

If it is a good idea, how can I add the identifier automatically to the header information. In other words, whenever the user calls the WCF method, the identifier must be automatically added to the header.

UPDATE: Clients that are using the WCF service are both Windows applications and Windows Mobile application (using Compact Framework).

Answer 1

The advantage to this is that it is applied to every call.

Create a class that implements IClientMessageInspector. In the BeforeSendRequest method, add your custom header to the outgoing message. It might look something like this:

public object BeforeSendRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel) {     HttpRequestMessageProperty httpRequestMessage;     object httpRequestMessageObject;     if (request.Properties.TryGetValue(HttpRequestMessageProperty.Name, out httpRequestMessageObject))     {         httpRequestMessage = httpRequestMessageObject as HttpRequestMessageProperty;         if (string.IsNullOrEmpty(httpRequestMessage.Headers[USER_AGENT_HTTP_HEADER]))         {             httpRequestMessage.Headers[USER_AGENT_HTTP_HEADER] = this.m_userAgent;         }     }     else     {         httpRequestMessage = new HttpRequestMessageProperty();         httpRequestMessage.Headers.Add(USER_AGENT_HTTP_HEADER, this.m_userAgent);         request.Properties.Add(HttpRequestMessageProperty.Name, httpRequestMessage);     }     return null; } 

Then create an endpoint behavior that applies the message inspector to the client runtime. You can apply the behavior via an attribute or via configuration using a behavior extension element.

Here is a great example of how to add an HTTP user-agent header to all request messages. I am using this in a few of my clients. You can also do the same on the service side by implementing the IDispatchMessageInspector.

Is this what you had in mind?

Update: I found this list of WCF features that are supported by the compact framework. I believe message inspectors classified as 'Channel Extensibility' which, according to this post, are supported by the compact framework.