c# - How to refactor such a big IF-ELSE statement -

i have such big if-else statement. how can refactor it? can give example how make more pretty? thanks!

public enum firestate {     none,     nonetominor,     minor,     minortonone,     minorrecovery,     minortomajor,     major,     majortonone,     majorrecovery }  private static firestate getfirestate(int previousrespincount, int currentrespincount, bool isrecovery) {     firestate fire = firestate.none;      if ((isrecovery || previousrespincount == 0) && currentrespincount < minorjackpotminrange)     {         fire = firestate.none;     }     else if (previousrespincount == 0 &&         (currentrespincount >= minorjackpotminrange         && currentrespincount < minorjackpotmaxrange))     {         fire = firestate.minorrecovery;     }     else if (isrecovery && currentrespincount >= minorjackpotmaxrange)     {         fire = firestate.majorrecovery;     }     else if (previousrespincount == (minorjackpotminrange - 1)         && currentrespincount == minorjackpotminrange)     {         fire = firestate.nonetominor;     }     else if (previousrespincount >= minorjackpotminrange         && (currentrespincount > 0 && currentrespincount < minorjackpotmaxrange))     {         fire = firestate.minor;     }     else if ((previousrespincount >= minorjackpotminrange &&         previousrespincount < minorjackpotmaxrange) &&         currentrespincount == 0)     {         fire = firestate.minortonone;     }     else if (previousrespincount == (minorjackpotmaxrange - 1)         && currentrespincount == minorjackpotmaxrange)     {         fire = firestate.minortomajor;     }     else if (previousrespincount >= minorjackpotmaxrange &&         currentrespincount >= minorjackpotmaxrange)     {         fire = firestate.major;     }     else if (previousrespincount >= minorjackpotmaxrange         && currentrespincount == 0)     {         fire = firestate.majortonone;     }      return fire; } 

you start writing unit tests; , use coverage come point sure understand paths through method. start refactor it, using known methods so; , tests tell you don't break while going forward.

finally, throw away of this; , restart tdd, , focus come reasonable design. in case: implement state machine ... using polymorphism; instead of cascaded if/else statements.

long story short: choices coverage-based refactoring; or if time allows, re-design whole component; current implementation state machine in poor disguise.