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

Question

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

public ActionResult GetAlbumPictures(int albumId)
{
    var album = AlbumRepo.GetSingle(album         


        

Answer 1

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);
}

Answer 2

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();

Answer 3

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 );
}

Answer 4

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/