//this goes where you're declaring variables
public Vector2 foo = Vector2.zero;

//this is what the switch statement would look like
switch (foo)
{
    case Vector2 v when v.Equals(Vector2.up):
        Debug.Log("Up");
        break;
    case Vector2 v when v.Equals(Vector2.left):
        Debug.Log("Left");
        break;
    case Vector2 v when v.Equals(Vector2.back):
        Debug.Log("Back");
        break;
}