WCF调用时怎么在请求中加自定义的头

WCF调用时如何在请求中加自定义的头
WCF用basicHttpBinding。
WSCalculateClient client = new WSCalculateSoapClient();
client.doSomeThing();
想在http请求中的头部加个cookie，该如何操作？
[解决办法]
http://stackoverflow.com/questions/964433/how-to-add-a-custom-header-to-every-wcf-calls/1408177#1408177

http://social.msdn.microsoft.com/Forums/en-US/biztalkgeneral/thread/96f24b06-76c7-4604-b946-8f3aa96f3b17/