How can I avoid AmbiguousMatchException between two controller actions?

Question

I have two controller actions with the same name but with different method signatures. They look like this:

    //
    // GET: /Stationery/5?asHtml=true
    [AcceptVerbs(HttpVerbs.Get)]
    public ContentResult Show(int id, bool asHtml)
    {
        if (!asHtml)
            RedirectToAction("Show", id);

        var result = Stationery.Load(id);
        return Content(result.GetHtml());
    }

    //
    // GET: /Stationery/5
    [AcceptVerbs(HttpVerbs.Get)]
    public XmlResult Show(int id)
    {
        var result = Stationery.Load(id);
        return new XmlResult(result);
    }

My unit tests have no issue with calling one or the other controller action, but my test html page throws a System.Reflection.AmbiguousMatchException.

<a href="/Stationery/1?asHtml=true">Show the stationery Html</a>
<a href="/Stationery/1">Show the stationery</a>

What needs to change to make this work?

Answer 1

Heres a link you may find userful. It talks about overloading the MVC Controllers.

Answer 2

There are two ways to address this:

1> Change the method name. 2> Provide different ActionName attributes to the two methods. You can define your own attribute.

Answer 3

There is the ActionName attribute. Take a look.

Answer 4

Just have one method like this.

[AcceptVerbs(HttpVerbs.Get)]
public ActionResult Show(int id, bool? asHtml)
{
    var result = Stationery.Load(id);

    if (asHtml.HasValue && asHtml.Value)
        return Content(result.GetHtml());
    else
        return new XmlResult(result);
}

Answer 5

To overcome this problem you can write an ActionMethodSelectorAttribute that examines the MethodInfo for each action and compares it to the posted Form values and then rejects any method for which the form values don't match (excluding the button name, of course).

Here's an example:- http://blog.abodit.com/2010/02/asp-net-mvc-ambiguous-match/

You could also make a simpler ActionMethodSelectorAttribute which looks only at the submit button name but that would tie your controller and view more closely.