WebApi attribute routing - Bind route parameter to an object for GETs

Question

Currently for every GET I have to manually create a query object from the route parameters.

Is it possible to bind directly to a query object instead?

So, instead of :

[Route("{id:int}")]
public Book Get(int id) {

    var query = new GetBookByIdQuery {
        Id = id
    };

    // execute query and return result
}

I could do this:

[Route("{id:int}")]
public Book Get(GetBookByIdQuery query) {
    // execute query and return result
}

Where GetBookByIdQuery looks like:

public class GetBookByIdQuery {
    public int Id { get; set;}
}

Answer 1

to read a complex type from the URI, [FromUri] can be used

    [Route("{id:int}")]
    public Book Get([FromUri] GetBookByIdQuery query) {

        // execute query and return result
    }

if you request api/values/2 then id property of query object will be 2;

Answer 2

The answer is to define you own HttpParameterBinding.

Here is the example I've made.

First I've created my CustomParameterBinding

public class CustomParameterBinding : HttpParameterBinding
{
    public CustomParameterBinding( HttpParameterDescriptor p ) : base( p ) { }

    public override System.Threading.Tasks.Task ExecuteBindingAsync( System.Web.Http.Metadata.ModelMetadataProvider metadataProvider, HttpActionContext actionContext, System.Threading.CancellationToken cancellationToken )
    {

        // Do your custom logic here
        var id = int.Parse( actionContext.Request.RequestUri.Segments.Last() );

        // Set transformed value
        SetValue( actionContext, string.Format( "This is formatted ID value:{0}", id ) );

        var tsc = new TaskCompletionSource<object>();
        tsc.SetResult(null );
        return tsc.Task;
    }
}

The next step is to create custom attribute to decorate parameter:

public class CustomParameterBindingAttribute : ParameterBindingAttribute
{
    public override HttpParameterBinding GetBinding( HttpParameterDescriptor parameter )
    {
        return new CustomParameterBinding( parameter );
    }
}

And finally now controller looks like:

public class ValuesController : ApiController
{
    // GET api/values/5
    [Route( "api/values/{id}" )]
    public string Get([CustomParameterBinding] string id )
    {
        return id;
    }       
}

So now when I call http://localhost:xxxx/api/values/5

I get: "This is formatted ID value:5"