WCF / ASMX :: Web Services: To Authenticate Sign Client Assembly?

I have an application that exposes a number of ASP.NET web services at an internet location. For security reasons, I want to be able to authenticate clients, and reject any that are not authorised. The authorised clients in question will be ASP.NET web applications,
but I do not have guaranteed access to their IIS configuration, nor to their local certificate stores, therefore the solution must not involve any of these items.

However, authorised clients, will always make calls to the web services using wrapper methods provided by an assembly that I
do have control over. My idea is to digitally sign that assembly, and use that signature as the basis for authenticating the client.For that to work, the assembly will need to be able to construct an X509Certificate object from itself, and to attach it to the call to the web service:

X509Certificate cert = X509Certificate.CreateFromSignedFile(Assembly.GetExecutingAssembly().Location);
_webService.ClientCertificates.Add(cert);

Then the web service must be able to compare the incoming request certificate to its own signing certificate to authenticate the client:

X509Certificate requestCert = new X509Certificate(Context.Request.ClientCertificate.Certificate);
X509Certificate signingCert = X509Certificate.CreateFromSignedFile(Assembly.GetExecutingAssembly().Location);[code]...

The documentation for the method doesn't help much, other than remarking that ASN.1 DER is the only certificate format supported by the method. if I am signing the assembly incorrectly, misunderstanding the method itself etc.? Or more generally if the approach I am taking will work or is flawed?