Is is possible to check if an object is already attached to a data context in Entity Framework?

I am getting the following error when trying to attach an object that is already attached to a given context via context.AttachTo(...):

An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.

Is there a way of achieving something along the lines of:

context.IsAttachedTo(...)

Cheers!

Edit:

The extension method Jason outlined is close, but it doesn't work for my situation.

I am trying to do some work using the method outlined in the answer to another question:

How do I delete one or more rows from my table using Linq to Entities *without* retrieving the rows first?

My code looks a bit like this:

var user = new User() { Id = 1 };
context.AttachTo("Users", user);
comment.User = user;
context.SaveChanges();

This works fine, except when I do something else for that user where I use the same method and try to attach a dummy User object. This fails because I have previously attached that dummy user object. How can I check for this?