How can I create a route constraint of type System.Guid?

Question

Can anyone point me in the right direction on how to map a route which requires two guids?

ie. http://blah.com/somecontroller/someaction/{firstGuid}/{secondGuid}

Answer 1

+1 @kazimanzurrashid. Seems spot on.

I'll give an alternative for those who haven't got C#4.0, of which Guid.TryParse is part of. There's another alternative with Regex but probably not worth the bother.

 public class GuidConstraint : IRouteConstraint
    {

        public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
        {
            if (values.ContainsKey(parameterName))
            {
                string stringValue = values[parameterName] as string;

                if (!string.IsNullOrEmpty(stringValue))
                {
                    //replace with Guid.TryParse when available.
                    try
                    {
                        Guid guid = new Guid(stringValue);
                        return true;
                    }
                    catch
                    {
                        return false;
                    }


                }
            }

            return false;
        }
    }