ClaimsPrincipalParameterBinding.cs

    public class ClaimsPrincipalParameterBinding : HttpParameterBinding
    {
        public ClaimsPrincipalParameterBinding(HttpParameterDescriptor descriptor)
            : base(descriptor)
        {
        }

        public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken)
        {
            ClaimsPrincipal claimsPrincipal = actionContext.Request.GetRequestContext().Principal as ClaimsPrincipal;
            actionContext.ActionArguments.Add(Descriptor.ParameterName, claimsPrincipal);

            return TaskHelpers.Completed();
        }
    }

configure.cs

        public static void Configure(HttpConfiguration configuration)
        {
            ConfigureParameterBindingRules(configuration.ParameterBindingRules);
        }

        private static void ConfigureParameterBindingRules(ParameterBindingRulesCollection bindingRules)
        {
            // If the parameter type is ClaimsPrincipal, use ClaimsPrincipalParameterBinding.
            bindingRules.Add(typeof(ClaimsPrincipal), descriptor => new ClaimsPrincipalParameterBinding(descriptor));
        }