webapi中的自定义路由约束

Custom Route Constraints

You can create custom route constraints by implementing the IHttpRouteConstraint interface. For example, the following constraint restricts a parameter to a non-zero integer value.

public class NonZeroConstraint : IHttpRouteConstraint
{
    public bool Match(HttpRequestMessage request, IHttpRoute route, string parameterName,
        IDictionary<string, object> values, HttpRouteDirection routeDirection)
    {
        object value;
        if (values.TryGetValue(parameterName, out value) && value != null)
        {
            long longValue;
            if (value is long)
            {
                longValue = (long)value;
                return longValue != 0;
            }

            string valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
            if (Int64.TryParse(valueString, NumberStyles.Integer,
                CultureInfo.InvariantCulture, out longValue))
            {
                return longValue != 0;
            }
        }
        return false;
    }
}

The following code shows how to register the constraint:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        var constraintResolver = new DefaultInlineConstraintResolver();
        constraintResolver.ConstraintMap.Add("nonzero", typeof(NonZeroConstraint));

        config.MapHttpAttributeRoutes(constraintResolver);
    }
}

Now you can apply the constraint in your routes:

[Route("{id:nonzero}")]
public HttpResponseMessage GetNonZero(int id) { ... }

You can also replace the entire DefaultInlineConstraintResolver class by implementing the IInlineConstraintResolver interface. Doing so will replace all of the built-in constraints, unless your implementation of IInlineConstraintResolver specifically adds them.