如何在Web API中禁止来自Get方法的post方法？

public class HttpMethodConstraint : IHttpRouteConstraint
{
    private readonly HttpMethod _allowedMethod;

    public HttpMethodConstraint(HttpMethod allowedMethod)
    {
        _allowedMethod = allowedMethod;
    }

    public bool Match(HttpRequestMessage request, IHttpRoute route, string parameterName, IDictionary<string, object> values, HttpRouteDirection routeDirection)
    {
        return request.Method == _allowedMethod;
    }
}

config.Routes.MapHttpRoute(
    name: "RestrictedApi",
    routeTemplate: "api/{controller}/{id}",
    defaults: new { id = RouteParameter.Optional },
    constraints: new { httpMethod = new HttpMethodConstraint(HttpMethod.Post) }
);