bankapp

console app

        static void Main(string[] args)
        {
            Console.WriteLine($"Enter 'accounts' to see a list of all current balances\nEnter 'log' to see the transaction log\nEnter a transfer command on format 'from -> to: amount' to make a transaction:");
            Console.WriteLine();
            while (true)
            {
                Console.Write("> ");
                var command = Console.ReadLine();
                if(command == "accounts")
                {
                    PrintAccounts();
                }
                else if (command == "log")
                {
                    PrintTransactionLog();
                }
                else
                {
                    var match = Regex.Match(command, @"(\w{1,}) *-> *(\w{1,}): *(\d{1,})");
                    if (match.Success)
                    {
                        Transfer(match.Groups[1].Value, match.Groups[2].Value, int.Parse(match.Groups[3].Value));
                    }
                    else
                    {
                        Console.WriteLine("Invalid command");
                    }
                }
                Console.WriteLine();
            }
        }

        private static void PrintAccounts() {}

        /// <summary>
        /// Prints the latest 10 entries of the transaction log
        /// </summary>
        private static void PrintTransactionLog() {}

        private static void Transfer(string fromCustomer, string toCustomer, int amount){}

sql schema and data

CREATE TABLE [dbo].[Account](
	[Balance] [int] NOT NULL CHECK(Balance >= 0),
	[AccountNo] [int] NOT NULL PRIMARY KEY CHECK  ((len([AccountNo])=(3) AND CONVERT([int],[AccountNo])>=(100))),
	[Customer] [nvarchar](10) NOT NULL UNIQUE
)

CREATE TABLE TransactionLog 
(
	Id INT IDENTITY(1,1) PRIMARY KEY,
	Moment DateTime NOT NULL,
	[From] INT NOT NULL REFERENCES Account (AccountNo),
	[To] INT NOT NULL REFERENCES Account (AccountNo),
	Amount INT NOT NULL CHECK(Amount>0)
)

INSERT INTO Account (AccountNo, Customer, Balance) VALUES (555, 'Andersson', 1000)
INSERT INTO Account (AccountNo, Customer, Balance) VALUES (123, 'Petterson', 5000);
INSERT INTO Account (AccountNo, Customer, Balance) VALUES (333, 'Lundström', 2000);
INSERT INTO Account (AccountNo, Customer, Balance) VALUES (999, 'Jag', 10000);