Nullability of reference types in type of parameter 'x' of 'int TxComparer.Compare(Transaction x, Transaction y)' doesn't match implicitly implemented member 'int IComparer<Transaction>.Compare(Transaction? x, Transaction? y)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'y' of 'int TxComparer.Compare(Transaction x, Transaction y)' doesn't match implicitly implemented member 'int IComparer<Transaction>.Compare(Transaction? x, Transaction? y)' (possibly because of nullability attributes).

Possible null reference return.

Converting null literal or possible null value to non-nullable type.

Possible null reference return.

Possible null reference argument for parameter 'item' in 'bool SortedSet<Transaction>.Remove(Transaction item)'.

Converting null literal or possible null value to non-nullable type.

Cannot convert null literal to non-nullable reference type.

Possible null reference return.