Elegantly reading in multiple inputs

I’m currently working on a game where I need to read in multiple inputs. I’m currently targetting the users to use a joystick when playing. What I need to do is execute a particular action when a particular input was pressed. For example,

if ( Input.GetButtonDown( "A" ) )
    //Do action A
else if (Input.GetButtonDown( "B" ) )
   //Do action B

Having 8 if statements (assuming I’m using the X A B Y button and the joysticks), is not great, but is accectable. It becomes an issue when I can combine these buttons to do a completely new action.

if(Input.GetButtonDown( "B" ) && Input.GetButtonDown( "A" )
    //Do another action AB

And currently I have 16 possible actions, but this can grow. Having 16+ if statements is not only ugly but hard to maintain. I was wondering if there is a better way to get multiple inputs.

Use Keycode.(key) instead of “B” and “A”.

For example:

Additionally, this is basically the only way to get actions and compare them. So if you are going to do every combination possible, you will need to make that many if statements comparing the input.