Why doesn't .NET have a SoftReference as well as a WeakReference, like Java?

I really love WeakReference's. But I wish there was a way to tell the CLR how much (say, on a scale of 1 to 5) how weak you consider the reference to be. That would be brilliant.

Java has SoftReference, WeakReference and I believe also a third type called a "phantom reference". That's 3 levels right there which the GC has a different behaviour algorithm for when deciding if that object gets the chop.

I am thinking of subclassing .NET's WeakReference (luckily and slightly bizzarely it isn't sealed) to make a pseudo-SoftReference that is based on a expiration timer or something.