Sort now tries to be consistent

If sort by is set to amount, try sorting by date if amounts are same.
For sorting by date, if dates are equal sort by id.
This should hopefully make the transactions order consistent.

This also means that SortTransactions will almost never return zero which is a good thing I believe.

NickvisionMoney.Shared/Controllers/AccountViewController.cs

@@ -410,19 +410,31 @@ private int SortTransactions(uint a, uint b)
         }
         else if (SortTransactionsBy == SortBy.Date)
         {
-            compareTo = _account.Transactions[a].Date.CompareTo(_account.Transactions[b].Date);
+            compareTo = GetCompareToByDate();
         }
         else if (SortTransactionsBy == SortBy.Amount)
         {
-            var aAmount = _account.Transactions[a].Amount * (_account.Transactions[a].Type == TransactionType.Income ? 1m : -1m);
-            var bAmount = _account.Transactions[b].Amount * (_account.Transactions[b].Type == TransactionType.Income ? 1m : -1m);
-            compareTo = aAmount.CompareTo(bAmount);
+            compareTo = GetCompareToByAmount();
         }
         if (!SortFirstToLast)
         {
             compareTo *= -1;
         }
         return compareTo;
+
+        int GetCompareToByDate()
+        {
+            var result = _account.Transactions[a].Date.CompareTo(_account.Transactions[b].Date);
+            return result == 0 ? a.CompareTo(b) : result; // If dates are equal, sort by id
+        }
+
+        int GetCompareToByAmount()
+        {
+            var aAmount = _account.Transactions[a].Amount * (_account.Transactions[a].Type == TransactionType.Income ? 1m : -1m);
+            var bAmount = _account.Transactions[b].Amount * (_account.Transactions[b].Type == TransactionType.Income ? 1m : -1m);
+            var result  = aAmount.CompareTo(bAmount);
+            return result == 0 ? GetCompareToByDate() : result; // If amounts are equal, sort by date
+        }
     }
 
     /// <summary>
@@ -628,15 +640,7 @@ public async Task AddTransactionAsync(Transaction transaction)
         if (res.Successful)
         {
             var transactions = _account.Transactions.Keys.ToList();
-            transactions.Sort((a, b) =>
-            {
-                var compareTo = SortTransactionsBy == SortBy.Date ? _account.Transactions[a].Date.CompareTo(_account.Transactions[b].Date) : a.CompareTo(b);
-                if (!SortFirstToLast)
-                {
-                    compareTo *= -1;
-                }
-                return compareTo;
-            });
+            transactions.Sort(SortTransactions);
             for (var i = 0; i < transactions.Count; i++)
             {
                 if (transactions[i] == transaction.Id)