With SelEx you can get the smallest expression selected around where the cursor is.

From there you can expand the selection to larger expressions, statements, and other C# syntax nodes.

I suggest you bind the expanding command on CTRL+UP and the reverting (collapsing) command on CTRL+DOWN.

SelEx doesn't register these itself, but it provides a command that does this. Hit CTRL+q and then type "register". You should see the command "Register SelEx keybindings". Choose to run this. This sets the keybinding globally. I haven't found a way yet to do this for C# only - if that annoys you, you'll have to bind the keys yourself.