C# connects to SQLite database and implements basic operations

string dbFilename =  "";
if (!(dbFilename))
{
    (dbFilename);
}

string connectionString = ("Data Source={0};Version=3;",dbFilename);
using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();//Open the database    ("123456");//Set password}

string connectionString =("Data Source={0}; Version=3; Password={1};",dbFilename,"123456");
using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();
}

using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();
string commandText = "CREATE TABLE IF NOT EXISTS Users (Id INTEGER PRIMARY KEY AUTOINCREMENT, Name VARCHAR(100), Code VARCHAR(100),Password VARCHAR(100))";

using (SQLiteCommand command = new SQLiteCommand(commandText, connection))
    {
        ();//Execute sql    }
}

using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();
string commandText = "insert into Users (Name, Code,Password) values (@name, @code,@password)";
using (SQLiteCommand command = new SQLiteCommand(commandText, connection))
    {
        // Set parameter values        ("@name", "administrator");
        ("@code", "admin");
        ("@password", "123456");
        // Execution statement        ();
    }
}

using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();
    string commandText = "update Users SET Password=@password WHERE Code = @code";
    using (SQLiteCommand command = new SQLiteCommand(commandText, connection))
    {
        // Set parameter values        ("@code", "admin");
        ("@password", "admin123456");
        // Execution statement        ();
    }
}

using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();
    string commandText  = "select * from Users";
    using (SQLiteCommand command = new SQLiteCommand(commandText, connection))
    {
        using (SQLiteDataReader reader = ())
        {
            while (())
            {
                ($"ID: {reader["Id"]}, name: {reader["Name"]}, coding: {reader["Code"]}");
            }
        }
    }
}

using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    ();
    string commandText = "delete from  Users where Code = @code";
    using (SQLiteCommand command = new SQLiteCommand(sql, connection))
    {
        // Set parameter values        ("@code", "admin");
        // Execution statement        ();
    }
}