Change text size in toast

Hello,

After much googling, I remained stumped on how to change the default text size of a toast. I found the following code:
ViewGroup group = (ViewGroup) toast.getView(); TextView messageTextView = (TextView) group.getChildAt(0); messageTextView.setTextSize(25);

Apparently this is all I need to do. However, in Xamarin when I type this code, I immediately get an error that says "the name 'toast' does not exist in the current context".

I imagine what I am trying to do is relatively simple, but I am (pathetically) quite stuck!

Any help would be greatly appreciated!

Dustin