Is it possible to change the querystring variable in ASP.NET MVC path before it hits the controller?

I have a controller method in ASP.NET MVC that looks like this:

public ActionResult GetAlbumPictures(int albumId)
{
    var album = AlbumRepo.GetSingle(albumId);
    var pictures = album.Pictures;
    return View(pictures);
}

The routing for this method looks like this:

routes.MapRoute(null,
                "pictures"
                new { controller = "Album", action = "GetAlbumPictures" });

The user will use the following URL to get the pictures, filtered by the album ID:

GET http://server/pictures?albumid=10

However, I'd like to change the querystring parameter to just album instead of albumid:

GET http://server/pictures?album=10

This would mean that the controller method needs to be modified to:

public ActionResult GetPictures(int album)
{
    ...
}

However, this is not ideal because now the method has a parameter named album, which can be confused as an Album object instead of the ID of the Album.

My question is, is there any way of configuring ASP.NET MVC so that in the routing, it will receive a querystring parameter called album, but then pass it off to the controller as the albumId parameter?

P.S. I know that I can do this in the routing table:

routes.MapRoute(null,
                "album/{albumId}/pictures",
                new { controller = "A开发者_StackOverflow社区lbum", action = "GetAlbumPictures" });

But due to legacy issues, I have to make it work for the querystring method as well.

You can create a custom action filter attribute to handle this scenario. I haven't tested this specific implementation, but the general idea is to do something like this:

public class AlbumAttribute : ActionFilterAttribute
    {
         public override void OnActionExecuting(ActionExecutingContext filterContext)
         {
             var albumId = filterContext.HttpContext.Request.QueryString["album"] as string;
             filterContext.ActionParameters["albumId"] = albumId;

             base.OnActionExecuting(filterContext);
         }
    }

Then, decorate your action method with the [Album] attribute:

[Album]
public ActionResult GetAlbumPictures(int albumId)
{
    var album = AlbumRepo.GetSingle(albumId);
    var pictures = album.Pictures;
    return View(pictures);
}

You can use a Custom Model Binder and it will work with both album and albumId. It can be implemented as follows:

Custom Model Binder:

public class AlbumModelBinder : IModelBinder
{
    public object BindModel
    (ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        int albumId;
        var albumVar = bindingContext.ValueProvider.GetValue( "album" );
        if (albumVar != null)
        {
            albumId = int.Parse( albumVar.AttemptedValue );
        }
        else
        {
            albumId = int.Parse( bindingContext.ValueProvider.GetValue( "albumId" ).AttemptedValue );
        }
        return albumId;
    }
}

Action implementation:

public ActionResult GetAlbumPictures
([ModelBinder( typeof( AlbumModelBinder ) )] int albumId)
{
    var album = AlbumRepo.GetSingle(albumId);
    var pictures = album.Pictures;
    return View(pictures);
} 

Global.asax.cs implementation:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    ModelBinders.Binders.Add( typeof( int ), new AlbumModelBinder() );
    RegisterRoutes( RouteTable.Routes );
}

Consider intercepting your request and use HttpContext.RewritePath to alter the query string before its picked up by the Routing engine. There is a nice diagram here showing how Url Rewriting is executed ages before the routing :)

http://learn.iis.net/page.aspx/496/iis-url-rewriting-and-aspnet-routing/

You can intercept the request before it hits the controller in Application_BeginRequest in your global.asax. You won't have access to the MVC contexts though, but could use

Server.Transfer(...);

or

Response.Redirect(...); 
Response.End();