ASP.Net Web API Return Specifc Error Data on Exception?

Question

.NET 4.5.2, with the following routing information setup:

public void Configuration( IAppBuilder appBuilder )
{
    var conf = new HttpConfiguration();
    conf.Routes.MapHttpRoute(
        name: "DefaultApi" ,
        routeTemplate: "service/2014/{controller}/{appKey}" , 
        defaults: new { appKey = RouteParameter.Optional }
    );
    appBuilder.UseWebApi( conf );
}

And with the following controller code:

public HttpResponseMessage Get( string appKey , string qs1 , string qs2 )
{
    var remess = new HttpResponseMessage { RequestMessage = Request , StatusCode = HttpStatusCode.OK };
    if ( true == new BusinessClass().ValueCheck( appKey , qs1 , qs2 ) )
    {
        remess.Content =  new StringContent( "1" , Encoding.UTF8 , "text/plain");
    }
    else
    {
        remess.Content =  new StringContent( "0" , Encoding.UTF8 , "text/plain");
    }
    return remess;
}

If I use this URI, it properly returns a "0" or a "1" based on the business logic:

http://localhost:963/service/2014/foo/appgo1?qs1=a&qs2=b

If I use this URI (leaving off the querystring values):

http://localhost:963/service/2014/foo/appgo1

I get a framework-controlled message:

<Error> <Message> No HTTP resource was found that matches the request
URI 'http://localhoost:963/service/2014/foo/appgo1'.
</Message> <MessageDetail> No action was found on the controller
'foo' that matches the request. </MessageDetail> </Error>

For this controller only, I would like to trap the fact that the querystring parameters are wrong and return a -1 instead. There is another controller that does not take querystring parameters at all, as well. Can anyone steer me in the right direction on this?

Thanks.

Answer 1

This is not the most elegant solution though it does work:

    public HttpResponseMessage Get(string appKey, string qs1 = null, string qs2 = null)
    {

        var remess = new HttpResponseMessage { RequestMessage = Request, StatusCode = HttpStatusCode.OK };

        if (qs1 == null || qs2 == null)
        {
            remess.Content = new StringContent("-1", Encoding.UTF8, "text/plain");
        }
        else if ( true == new BusinessClass().ValueCheck( appKey , qs1 , qs2 ) )
        {
            remess.Content = new StringContent("1", Encoding.UTF8, "text/plain");
        }
        else
        {
            remess.Content = new StringContent("0", Encoding.UTF8, "text/plain");
        }
        return remess;

    }

You basically make the query string params optional and then check if either is null to return your -1 code. Otherwise, do your business logic checks.

You could also have a default GET action to catch all gets to the controller and return -1 there.