public bool Exists(ModelBase obj) { if (obj is Account) { return(Accounts.Contains(obj)); } else if (obj is Transaction) { return(Transactions.Contains(obj)); } else if (obj is TransactionDetail) { return(TransactionDetails.Contains(obj)); } else if (obj is Receipt) { return(Receipts.Contains(obj)); } else if (obj is ScheduledTransaction) { return(ScheduledTransactions.Contains(obj)); } else if (obj is ScheduledTransactionDetail) { return(ScheduledTransactionDetails.Contains(obj)); } else if (obj is Category) { return(Categories.Contains(obj)); } else if (obj is Product) { return(Products.Contains(obj)); } else { return(false); } }