MVC Pro Tip: Don't use the "id" URL parameter in your routes

By default, MVC will use a route layout like this:

routes.MapRoute(
    "Default", // Route name
    "{controller}/{action}/{id}", // URL with parameters
    new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);

Besides the fact that you shouldn't use the default route (use named routes!), there's another issue.

Do you have any domain models like this?

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

Now, let's say you wanted to add a new Edit method for this model:

public FooController {
    [HttpPost]
    public ActionResult Edit(int id, Foo foo) {

    }
}

There will be a problem here if you expect to be able to change this ID (rare but it happens). MVC will model bind the route's id parameter to your model's ID, possibly breaking your code. This is because MVC does not differentiate your two id and Id parameters, it sees them as one in the same (this has to do with the underlying Request collection).

Fix it!

It's simple to fix. Instead of using id as a URL parameter throughout your application, use something else! I typically use identifier:

routes.MapRoute(
    "Default", // Route name
    "{controller}/{action}/{identifier}", // URL with parameters
    new { controller = "Home", action = "Index", identifier = UrlParameter.Optional } // Parameter defaults
);

// Controller
public FooController {
    [HttpPost]
    public ActionResult Edit(int identifier, Foo foo) {

    }
}

Voila. No more model binding issues!