c# check for a poker straight -

i trying write poker hand evaluation method in c#. have managed every poker hand using linq except straight. don't play straight made of 5 cards increments of 1 each card. ace can high or low.

i have created object called card has suit, rank , value (j = 11, q =12 etc..). method passed list of object containing 7 cards (hole cards , board.)

another thing bear in mind straight can made if player has 5 or 10.

see below methods other poker hands , please let me know if have idea straight method. pseudo code fine also.

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public bool checkpair(list<card> cards) {     //see if 2 cards card same rank.     return cards.groupby(card => card.rank).count(group => group.count() == 2) == 1; }  public bool checktwopair(list<card> cards) {     //see if there 2 lots of 2 cards card same rank.     return cards.groupby(card => card.rank).count(group => group.count() >= 2) == 2; }  public bool checktrips(list<card> cards) {     //see if 3 cards card same rank.     return cards.groupby(card => card.rank).any(group => group.count() == 3); } public bool checkstraight(list<card> cards) {     // order decending see order     var cardsinorder = cards.orderbydescending(a => a.value).tolist();     // check ace can high , low     if (cardsinorder.first().rank == "a")     {         // check if straight ace has has 2 values         bool highstraight = cards.where(a => a.rank == "k" || a.rank == "q" || a.rank == "j" || a.rank == "10").count() == 4;         bool lowstraight = cards.where(a => a.rank == "2" || a.rank == "3" || a.rank == "4" || a.rank == "5").count() == 4;         // return true if straight ace         if (lowstraight == true || highstraight == true)         {             return true;         }     }     else     {         // check straight here         return true;     }     // no straight if reached here.     return false;  }  public bool checkflush(list<card> cards) {     //see if 5 or more cards card same rank.     return cards.groupby(card => card.suit).count(group => group.count() >= 5) == 1; }  public bool checkfullhouse(list<card> cards) {     // check if trips , pair true     return checkpair(cards) && checktrips(cards); } public bool checkquads(list<card> cards) {     //see if 4 cards card same rank.     return cards.groupby(card => card.rank).any(group => group.count() == 4); }  // need check same 5 cards public bool checkstraightflush(list<card> cards) {     // check if flush , straight true.     return checkflush(cards) && checkstraight(cards); } 

this might not best performing check, i'd it's readable property.

just grab 5 cards, skipping cards you've seen every iteration , check straight each sequence. ordered sequence straight if not contain doubles , if first , last cards difference 5.

public bool checkstraight(list<card> cards) {      //maybe check 5 , 10 here first performance       var ordered = cards.orderbydescending(a => a.value).tolist();      for(i = 0; < ordered.count - 5; i++) {           var skipped = ordered.skip(i);           var possiblestraight = skipped.take(5);           if(isstraight(possiblestraight)) {                return true;           }      }      return false; }  public bool isstraight(list<card> fiveorderedcards) {      var doubles = cards.groupby(card => card.rank).count(group => group.count() > 1);      var inarow = cards[4] - cards[0] = 5; //ace 0       return !doubles && inarow; }