How to add a custom header to every WCF calls?

Question

Hi, 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. I mean whenever user called the WCF method the identifier 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

You add it to the call using:

using (OperationContextScope scope = new OperationContextScope((IContextChannel)channel))
{
    MessageHeader<string> header = new MessageHeader<string>("secret message");
    var untyped = header.GetUntypedHeader("Identity", "http://www.my-website.com");
    OperationContext.Current.OutgoingMessageHeaders.Add(untyped);

    // now make the WCF call within this using block
}

And then, server-side you grab it using:

MessageHeaders headers = OperationContext.Current.IncomingMessageHeaders;
string identity = headers.GetHeader<string>("Identity", "http://www.my-website.com");

Answer 2

Context bindings in .NET 3.5 might be just what you're looking for. There are three out of the box: BasicHttpContextBinding, NetTcpContextBinding, and WSHttpContextBinding. Context protocol basically passes key-value pairs in the message header. Check out Managing State With Durable Services article on MSDN magazine.

Answer 3

If I understand your requirement correctly, the simple answer is: you can't.

That's because the client of the WCF service may be generated by any third party that uses your service.

IF you have control of the clients of your service, you can create a base client class that add the desired header and inherit the behavior on the worker classes.

Answer 4

You can specify custom headers in the MessageContract.

You can also use < endpoint> headers that are stored in the configuration file and will be copied allong in the header of all the messages sent by the client/service. This is usefull to add some static header easily.

Answer 5

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.

Answer 6

Hi Mohammed and Mark

I am trying to achieve the same thing but with the limitations of CF I am unable to move forward.

Have you by any chance got this to work? Could you please update the forum on the status so that it would be useful for other fellow developers?

Answer 7

If you just want to add the same header to all the requests to the service, you can do it with out any coding!
Just add the headers node with required headers under the endpoint node in your client config file

<client>
<endpoint address="http://localhost/..." >
<headers>
<HeaderName>Value</HeaderName>
</headers>
</endpoint>