No, you can't, because the whole point of if/else is to do one thing if an expression is TRUE and another if the expression is FALSE. If you want to execute both blocks of code then you need to rejig the expression, for example instead of
Code:
if (test) { ... }
else { ... }
which is almost equivalent to
Code:
if (test) { ... }
if (!test) { ... }
(almost, because in this construction you could set test to FALSE in the first if block and cause the second to be executed), whereas if/else doesn't allow for that) you could use
Code:
if (test || do_both) { ... }
if (!test || do_both) { ... }