How to get all active parameters in ASP.NET MVC (2)

Question

I was wondering whether there is a way to create an ActionLink or similar, that changes only a few parameters of the actual query, and keeps all the other parameters intact. For example if I'm on an URL like http://example.com/Posts/Index?Page=5&OrderBy=Name&OrderDesc=True I want to change only the Page , or OrderBy parameter and keep all other parameters the same, even those I don't yet know of (like when I want to add a Search parameter or something similar too).

The header of my current action looks like this:

public ActionResult Index(int? Page, string OrderBy, bool? Desc)

and I'm only interested in the values that this controller "eats". I want however that when I extend this action (for example with a string Search parameter) the links should work the same way as before.

Here is what I did already:

1. Create a new RouteValueDictionary and fill it with everything from RouteData.Values
   • Problem: This only fills the parameters that are used in the Routing, so all other optional parameters (like Page ) to the controller are lost
2. Add everything from HttpContext.Request.QueryString to the previous dictionary
   • This is what I am currently using
   • Problem: It might have some junk stuff, that the Controller didn`t ask for, and it doesn't work if the page was loaded using POST. You also don't have any ModelBindings (but this isn't much of a problem, because we are re-sending everything anyway)
3. Use HttpContext.Request.Params
   • Problem: this has too much junk data which imho one shouldn't add to a RouteValueDictionary that is passed to an ActionLink

So the questions:

1. Is there an RVD that has all the data that was passed to the Controller and was used by it?
2. Is this solution good, or are there any caveats I didn't think about (mainly in the context of changing a few query parameters while keeping the others intact)?
3. Is there a way to filter out the "junk" data from the Params object?

EDIT: Checked the RouteData.DataTokens variable, but it's usually empty, and doesn't contain everything I need. It seems to only contain parameters that are needed for the routing somewhere, but not all of the parameters.

Answer 1

Have a look in RouteData.DataTokens .

RouteData.DataTokens @ MSDN documentation :

Gets a collection of custom values that are passed to the route handler but are not used when ASP.NET routing determines whether the route matches a request.

HTHs,
Charles