### Instruction:
Develop a C# application that simulates a simple ATM machine. Users should be able to create accounts, deposit and withdraw money, and check their account balance. Store account information in a local SQLite database and ensure proper validation and error handling for user inputs.


### Response:

To create a simple ATM machine simulation in C#, you'll need to follow these steps:

1. Install SQLite package
2. Create an Account class
3. Set up the database connection and table creation
4. Implement account creation, deposit, withdrawal, and balance checking methods
5. Add user input validation and error handling

Here's a sample implementation of this application:

1. First, install the `System.Data.SQLite` NuGet package by running the following command in your project directory:

```
dotnet add package System.Data.SQLite
```

2. Create an `Account` class with properties for the account number, name, and balance:

```csharp
public class Account
{
    public int AccountNumber { get; set; }
    public string Name { get; set; }
    public decimal Balance { get; set; }
}
```

3. Set up the database connection and table creation:

```csharp
using System;
using System.Data;
using System.Data.SQLite;

namespace SimpleATM
{
    public static class Database
    {
        private const string ConnectionString = "Data Source=accounts.db";

        public static void Initialize()
        {
            using var connection = new SQLiteConnection(ConnectionString);
            connection.Open();

            using var command = new SQLiteCommand(connection);
            command.CommandText = @"CREATE TABLE IF NOT EXISTS accounts (
                                        account_number INTEGER PRIMARY KEY,
                                        name TEXT NOT NULL,
                                        balance REAL NOT NULL)";
            command.ExecuteNonQuery();
        }
    }
}
```

4. Implement account creation, deposit, withdrawal, and balance checking methods:

```csharp
using System;
using System.Data;
using System.Data.SQLite;

namespace SimpleATM
{
    public static class AccountManager
    {
        private const string ConnectionString = "Data Source=accounts.db";

        public static Account CreateAccount(string name)
        {
            using var connection = new SQLiteConnection(ConnectionString);
            connection.Open();

            using var command = new SQLiteCommand(connection);
            command.CommandText = "INSERT INTO accounts (name, balance) VALUES (@name, 0)";
            command.Parameters.AddWithValue("@name", name);
            command.ExecuteNonQuery();

            return GetAccountByName(name);
        }

        public static Account GetAccount(int accountNumber)
        {
            using var connection = new SQLiteConnection(ConnectionString);
            connection.Open();

            using var command = new SQLiteCommand(connection);
            command.CommandText = "SELECT * FROM accounts WHERE account_number = @accountNumber";
            command.Parameters.AddWithValue("@accountNumber", accountNumber);

            using var reader = command.ExecuteReader();
            if (!reader.Read())
            {
                return null;
            }

            return new Account
            {
                AccountNumber = reader.GetInt32(0),
                Name = reader.GetString(1),
                Balance = reader.GetDecimal(2)
            };
        }

        public static Account GetAccountByName(string name)
        {
            using var connection = new SQLiteConnection(ConnectionString);
            connection.Open();

            using var command = new SQLiteCommand(connection);
            command.CommandText = "SELECT * FROM accounts WHERE name = @name";
            command.Parameters.AddWithValue("@name", name);

            using var reader = command.ExecuteReader();
            if (!reader.Read())
            {
                return null;
            }

            return new Account
            {
                AccountNumber = reader.GetInt32(0),
                Name = reader.GetString(1),
                Balance = reader.GetDecimal(2)
            };
        }

        public static void Deposit(Account account, decimal amount)
        {
            using var connection = new SQLiteConnection(ConnectionString);
            connection.Open();

            using var command = new SQLiteCommand(connection);
            command.CommandText = @"UPDATE accounts 
                                    SET balance = balance + @amount 
                                    WHERE account_number = @accountNumber";
            command.Parameters.AddWithValue("@amount", amount);
            command.Parameters.AddWithValue("@accountNumber", account.AccountNumber);
            command.ExecuteNonQuery();
        }

        public static bool Withdraw(Account account, decimal amount)
        {
            if (account.Balance < amount)
            {
                return false;
            }

            using var connection = new SQLiteConnection(ConnectionString);
            connection.Open();

            using var command = new SQLiteCommand(connection);
            command.CommandText = @"UPDATE accounts 
                                    SET balance = balance - @amount 
                                    WHERE account_number = @accountNumber";
            command.Parameters.AddWithValue("@amount", amount);
            command.Parameters.AddWithValue("@accountNumber", account.AccountNumber);
            command.ExecuteNonQuery();

            return true;
        }
    }
}
```

5. Add user input validation and error handling:

```csharp
using System;

namespace SimpleATM
{
    class Program
    {
        static void Main(string[] args)
        {
            Database.Initialize();

            Console.WriteLine("Welcome to the Simple ATM!");
            Console.Write("Enter your name: ");
            string name = Console.ReadLine();

            Account account = AccountManager.GetAccountByName(name) ?? AccountManager.CreateAccount(name);

            while (true)
            {
                Console.WriteLine("\nChoose an option:");
                Console.WriteLine("1. Check balance");
                Console.WriteLine("2. Deposit");
                Console.WriteLine("3. Withdraw");
                Console.WriteLine("4. Exit");

                int choice = int.Parse(Console.ReadLine());

                switch (choice)
                {
                    case 1:
                        account = AccountManager.GetAccount(account.AccountNumber);
                        Console.WriteLine($"Your current balance is: {account.Balance:C}");
                        break;
                    case 2:
                        Console.Write("Enter deposit amount: ");
                        decimal depositAmount = decimal.Parse(Console.ReadLine());
                        AccountManager.Deposit(account, depositAmount);
                        Console.WriteLine($"Deposited {depositAmount:C} successfully.");
                        break;
                    case 3:
                        Console.Write("Enter withdrawal amount: ");
                        decimal withdrawalAmount = decimal.Parse(Console.ReadLine());
                        if (AccountManager.Withdraw(account, withdrawalAmount))
                        {
                            Console.WriteLine($"Withdrew {withdrawalAmount:C} successfully.");
                        }
                        else
                        {
                            Console.WriteLine("Insufficient balance for withdrawal.");
                        }
                        break;
                    case 4:
                        Console.WriteLine("Goodbye!");
                        return;
                }
            }
        }
    }
}
```

This implementation provides a simple console application that simulates an ATM machine. Users can create accounts, deposit and withdraw money, and check their account balance. Account information is stored in a local SQLite database, and proper validation and error handling are implemented for user inputs.