How can I add characters at the end of my xml response? - web-services

Question

I have a restful web service that's returning results like this:
<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">Some Text</string>
However, the people on the receiving end need this text to be terminated w/ a special character such as "\r". How can I add that text to the end of my serialized response?
I'm sending this response from inside of a WCF service in C# like this:
[WebGet(UriTemplate = "/MyMethod?x={myId}"), OperationContract]
string GetSomeText(Guid myId);

Answer 1

I can think of three solutions:
1. Http Module (least code but most confusing for maintenance)
Assuming you're hosting your WCF in ASP.Net, you can create an Http module to add a \r to the end of all responses in your application.
This could be the code of the Http module. I've used 'End' as a suffix here because it's easier to read in a browser than \r, but for \r you would change the "End" in context_PostRequestHandlerExecute to "\r".
public class SuffixModule : IHttpModule
{
private HttpApplication _context;
public void Init(HttpApplication context)
{
_context = context;
_context.PostRequestHandlerExecute += context_PostRequestHandlerExecute;
}
void context_PostRequestHandlerExecute(object sender, EventArgs e)
{
// write the suffix if there is a body to this request
string contentLengthHeaderValue = _context.Response.Headers["Content-length"];
string suffix = "End";
if (!String.IsNullOrEmpty(contentLengthHeaderValue))
{
// Increase the content-length header by the length of the suffix
_context.Response.Headers["Content-length"] =
(int.Parse(contentLengthHeaderValue) + suffix.Length)
.ToString();
// and write the suffix!
_context.Response.Write(suffix);
}
}
public void Dispose()
{
// haven't worked out if I need to do anything here
}
}
Then you need to set up your module up in your web.config. The below assumes you have IIS running in Integrated Pipeline mode. If you haven't, you need to register the modules in the <system.web><httpModules> section.
<system.webServer>
<modules runAllManagedModulesForAllRequests="true">
<!-- 'type' should be the fully-qualified name of the type,
followed by a comma and the name of the assembly-->
<add name="SuffixModule" type="WcfService1.SuffixModule,WcfService1"/>
</modules>
</system.webServer>
This option has the problems that it would affect all requests in your application by default and it would probably fall over if you decided to use chunked encoding.
2. Use ASP.NET MVC (changes technology but good maintainability)
Use MVC instead of WCF. You'd have far better control over your output.
3. Custom Serializer (lots of code, but less hacky than option 1)
You could write your own custom serializer. This StackOverflow question gives you pointers on how to do this. I didn't write a prototype for this because it looked as though there were many, many methods which needed to be overridden. I daresay most of them would be pretty simple delegations to the standard serializer.