Customize MapHttpAttributeRoutes for Web Api Versioning

Question

I am implementing Web API versioning as in Web API Versioning. My controllers are in 2 separate namespaces, and I\'ve used a custom SelectController method to choose which versi

Answer 1

Here is a solution that will let you use the Web API 2 way of versioned routes (headers), in addition to query parameter support (i.e. use a header called 'api-version' or a querystring parameter named '?api-version=XXX'.

The HTTP Route constraint does the work:

/// 

/// Add a route constraint to detect version header or by query string
/// 
public class RouteVersionHttpConstraint : IHttpRouteConstraint
{
    public const string VersionHeaderName = "api-version";
    private const int DefaultVersion = 1;
    /// 

    /// Add a route constraint to detect version header or by query string
    /// 
    /// 
    public RouteVersionHttpConstraint(int allowedVersion)
    {
        AllowedVersion = allowedVersion;
    }

    public int AllowedVersion
    {
        get;
        private set;
    }

    /// 

    /// Perform the controller match
    /// 
    /// 
    /// 
    /// 
    /// 
    /// 
    /// 
    public bool Match(HttpRequestMessage request, IHttpRoute route, string parameterName, IDictionary values, HttpRouteDirection routeDirection)
    {
        if (routeDirection == HttpRouteDirection.UriResolution)
        {
            int version = GetVersionHeaderOrQuery(request) ?? DefaultVersion;
            if (version == AllowedVersion)
            {
                return true;
            }
        }
        return false;
    }

    /// 

    /// Check the request header, and the query string to determine if a version number has been provided
    /// 
    /// 
    /// 
    private int? GetVersionHeaderOrQuery(HttpRequestMessage request)
    {
        string versionAsString;
        IEnumerable headerValues;
        if (request.Headers.TryGetValues(VersionHeaderName, out headerValues) && headerValues.Count() == 1)
        {
            versionAsString = headerValues.First();
            int version;
            if (versionAsString != null && Int32.TryParse(versionAsString, out version))
            {
                return version;
            }
        }
        else
        {
            var query = System.Web.HttpUtility.ParseQueryString(request.RequestUri.Query);
            string versionStr = query[VersionHeaderName];
            int version = 0;
            int.TryParse(versionStr, out version);
            if (version > 0)
                return version;
        }
        return null;
    }
}

And the route factory:

/// 

/// Versioning support for the WebAPI controllers
/// 
public class RouteVersionAttribute : RouteFactoryAttribute
{
    public int Version { get; private set; }

    public RouteVersionAttribute() : this(null, 1) 
    { 
    }
    /// 

    /// Specify a version for the WebAPI controller
    /// 
    /// 
    public RouteVersionAttribute(int version) : this(null, version)
    {
    }

    public RouteVersionAttribute(string template, int version)
        : base(template)
    {
        Version = version;
    }

    public override IDictionary Constraints
    {
        get
        {
            var constraints = new HttpRouteValueDictionary();
            constraints.Add("version", new RouteVersionHttpConstraint(Version));
            return constraints;
        }
    }

    public override IDictionary Defaults
    {
        get
        {
            var defaults = new HttpRouteValueDictionary();
            defaults.Add("version", 1);
            return defaults;
        }
    }

}

Usage:

[RouteVersion("api/versiontest", 1)]
public class Version1TestController : BaseApiController
{
    // get: api/versiontest
    [HttpGet]
    public HttpResponseMessage get()
    {
        return Request.CreateResponse(HttpStatusCode.OK, new { Version = "API Version 1 selected" });
    }

}

[RouteVersion("api/versiontest", 2)]
public class Version2TestController : ApiController
{
    // get: api/versiontest
    [HttpGet]
    public HttpResponseMessage get()
    {
        return Request.CreateResponse(HttpStatusCode.OK, new { Version = "API Version 2 selected" });
    }

}