/// <summary>
        /// Declare the extension method given the function container class.
        /// </summary>
        /// <param name="functionExtensionClass">Function container class</param>
        /// <param name="func">Function to add</param>
        protected virtual void DeclareExtensionMethod(CodeTypeDeclaration functionExtensionClass, Function func)
        {
            // retrieve parameters and add the extension method
            ServiceOperationAnnotation actionAnnotation = func.Annotations.OfType<ServiceOperationAnnotation>().Single();
            ExceptionUtilities.Assert(actionAnnotation.BindingKind.IsBound(), "Action function cannot generate extension method with out function having a binding");
            FunctionParameter bindingTypeParameter = func.Parameters[0];

            CodeMemberMethod method = functionExtensionClass.AddExtensionMethod(
                func.Name,
                new CodeParameterDeclarationExpression(
                    this.GetParameterTypeOrFunctionReturnTypeReference(bindingTypeParameter.Annotations, bindingTypeParameter.DataType),
                    bindingTypeParameter.Name));

            // add non-binding type parameters
            foreach (var parameter in func.Parameters.Where(p => p.Name != bindingTypeParameter.Name))
            {
                method.Parameters.Add(
                    new CodeParameterDeclarationExpression(
                        this.GetParameterTypeOrFunctionReturnTypeReference(parameter.Annotations, parameter.DataType),
                        parameter.Name));
            }

            // throw exception if the client code method is called
            method.Statements.Add(
                new CodeThrowExceptionStatement(
                    new CodeObjectCreateExpression(
                        new CodeTypeReference(typeof(InvalidOperationException)),
                        new CodeExpression[] { })));

            // add method return type
            if (func.ReturnType != null)
            {
                method.ReturnType = this.GetParameterTypeOrFunctionReturnTypeReference(func.Annotations, func.ReturnType);
            }
        }