Get Animator Blend Tree

Just wondering, is it possible to get the Blend tree of an Animator?

I want to play a random animation from the Blend Tree but I want the code to be as flexible as possible. Some sudo code for the concept I am looking for is:

Code (CSharp):

1. int rng = Random.Range(0, BlendTree.Length);
2.  
3. _anim.SetFloat("RandomAnimation", rng);

Is this possible? Or do I have to set parameters for the random number directly?

Thanks for your time!