Accessing API on different domain with CORS - wcf

Question

I am working on a self-hosted WCF service with some GET and POST methods,
For Example
[OperationContract]
[WebInvoke(Method = "GET", BodyStyle = WebMessageBodyStyle.Wrapped)]
public string HelloWorld(){
....
}
[OperationContract]
[WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Wrapped)]
public string GetMessage(string username){
....
}
when accessing those services on the client side which is hosted on different domain, I have got the following error
No 'Access-Control-Allow-Origin' header is present on the requested
resource. Origin 'http://localhost:57805' is therefore not allowed
access. The response had HTTP status code 400.
After researching on the Internet, I figured that the error can be resolved by putting the following codes in each WCF function
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Allow-Origin", "*");
if (WebOperationContext.Current.IncomingRequest.Method == "OPTIONS")
{
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Allow-Header", "Content-Type, Accept, SOAPAction");
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Allow-Credentials", "false");
}
Now this block of code is working great for a GET method, so I can see there is "Access-Control-Allow-Origin" added into the response header. However it does not work for a POST method somehow as the response header has no change at all.
Does anyone have an idea why it is not working for a POST method?
I have changed the GetMessage to be a GET method, the response header worked immediately but not when I changed it back to POST

Answer 1

The problem is resolved!!
The code works great for both GET and POST, however the web service throw the following error for my POST function, therefore it causes a failure.
The OperationFormatter could not deserialize any information from the
Message because the Message is empty (IsEmpty = true).
By changing the BodyStyle for the function to WrappedResponse, the error gone and the function can be accessed outside the domain
[OperationContract]
[WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.WrappedResponse)]
Booking CreateNewBooking(int divisionId);