}//end makeWithdrawal method
/// <summary>
/// Account transaction for Current Account.
/// Withdraws a specified amount from the account and saves the changes in the database.
/// Amount to be withdrawn will be more than the account balance.(Overdraft).
/// Requires: The amount to be withdrawn is more than the current account balance.
/// Requires: The account number is valid.
/// Requires: The account balance value is positive.
/// </summary>
/// <param name="Accountnumber">Number identifying account</param>
/// <param name="amount">the amount to withdraw</param>
/// <exception cref="ArgumentException">Thrown when the amount to withdraw can be withdrawn without overdraft or,
/// when the input account number is not same as
/// the account number registered for the account.</exception>
/// <returns>The new account balance</returns>
public double overdraftWithdraw(string Accountnumber, double amount)
{
//overdraft allows withdrawal to exceed the account balance
Contract.Requires <ArgumentException>(this.AccountBalance > 0, "You already owe the bank");
Contract.Requires <ArgumentException>(amount > this.AccountBalance, "Cannot use overdraft. Withdraw the normal way");
Contract.Requires <ArgumentException>(this.AccountNumber.Equals(Accountnumber), "Invalid account number, check again");
Contract.Ensures(Contract.OldValue <double>(this.AccountBalance) > this.AccountBalance);
Contract.Ensures((Contract.OldValue <double>(this.AccountBalance) - amount).Equals(this.AccountBalance));
Contract.Ensures(this.AccountBalance < 0);
this.AccountBalance = this.AccountBalance - amount; //negative balance due to overdraft
BankDatabaseEngine.DebitAccount(Accountnumber, amount); //debit the account in the database
return(this.AccountBalance);
} //end overDraft method
}//end makeDeposit method
/// <summary>
/// Current Account transaction. Withdraws a specified amount from the current account and saves the changes in the database.
/// Requires: The amount to be withdrawn should not be negative
/// Requires: The amount to be withdrawn should be less than or equal to the account balance
/// Requires: The account balance should be more than the minimum balance allowed for the bank
/// Requires: The account number is valid
/// </summary>
/// <param name="Accountnumber">Number identifying account</param>
/// <param name="amount">the amount to withdraw</param>
/// <exception cref="ArgumentException">Thrown when the account balance is not sufficient for the transaction or,
/// when the amount to withdraw is negative or,
/// when the input account number is not same as
/// the account number registered for the account.</exception>
/// <returns>The new account balance</returns>
public override double makeWithdrawal(string Accountnumber, double amount)
{
Contract.Requires <ArgumentException>(amount > 0, "Invalid amount. Please check input");
Contract.Requires <ArgumentException>(amount <= (AccountBalance - BankPolicy.minimumcurrentBalance), "Cannot withdraw more than the available balance");
Contract.Requires <ArgumentException>(AccountBalance >= BankPolicy.minimumcurrentBalance, "Account balance is Insufficient for this transaction");
Contract.Requires <ArgumentException>(AccountNumber.Equals(Accountnumber), "Invalid account number, check again");
Contract.Ensures(AccountBalance >= BankPolicy.minimumcurrentBalance);
Contract.Ensures(Contract.OldValue <double>(AccountBalance) > AccountBalance);
Contract.Ensures((Contract.OldValue <double>(AccountBalance) - amount).Equals(AccountBalance));
AccountBalance = AccountBalance - amount;
// Debit the account in the database
BankDatabaseEngine.DebitAccount(Accountnumber, amount);
return(AccountBalance);
}//end makeWithdrawal method