Database.cs

using System.Collections.Generic;
using System.Data.SqlClient;

namespace SunTripsLin
{
    class Database
    {
        // [IMPORTANT] Connection string: used to connect to the DB, make sure you replace "SunTrips" with your database name!!
        private readonly string connectionString = "Data Source=localhost;Initial Catalog=SunTrips;Integrated Security=True";

        /// <summary>
        /// Gets a list of all users from the database
        /// </summary>
        /// <returns>A list of Users</returns>
        public List<User> GetAllUsers()
        {
            string sqlQuery = "SELECT * FROM [User]"; // Query to run against the DB

            List<User> users = new List<User>(); // Start with an ampty list of users

            using (SqlConnection myConnection = new SqlConnection(connectionString)) // Prepare connection to the db
            {
                SqlCommand sqlCommand = new SqlCommand(sqlQuery, myConnection); // Prepare the query for the db

                myConnection.Open(); // Open connection to the db

                using (SqlDataReader dataReader = sqlCommand.ExecuteReader()) // Run query on db
                {
                    while (dataReader.Read()) // Read response from db (all rows)
                    {
                        User user = new User(); // create new User object

                        user.Id = int.Parse(dataReader["Id"].ToString()); // Set user Id from db
                        user.Username = dataReader["Username"].ToString(); // Set user Username from db
                        user.Password = dataReader["Password"].ToString(); // Set user Password from db

                        users.Add(user); // Add last user to list of users
                    }

                    myConnection.Close(); // Close connection to the db
                }
            }

            return users; // Return all users
        }

        /// <summary>
        /// Returns the first user in the database with a matching Username
        /// </summary>
        /// <param name="username">Username to match in the db</param>
        /// <returns>A User</returns>
        public User GetUserByUsername(string username)
        {
            string sqlQuery = "SELECT * FROM [User] WHERE [Username] LIKE @username"; // Query to run against the DB

            User user = null; // Create a new user without any value

            using (SqlConnection myConnection = new SqlConnection(connectionString)) // Prepare connection to the db
            {
                SqlCommand sqlCommand = new SqlCommand(sqlQuery, myConnection); // Prepare the query for the db

                sqlCommand.Parameters.AddWithValue("@username", username); // Add username to the query 

                myConnection.Open(); // Open connection to the db

                using (SqlDataReader dataReader = sqlCommand.ExecuteReader()) // Run query on db
                {
                    if (dataReader.Read()) // Read response from db (first row)
                    {
                        user = new User(); // create new User object

                        user.Id = int.Parse(dataReader["Id"].ToString()); // Set user Id from db
                        user.Username = dataReader["Username"].ToString(); // Set user Username from db
                        user.Password = dataReader["Password"].ToString(); // Set user Password from db

                    }

                    myConnection.Close(); // Close connection to the db
                }
            }

            return user; // Return the user
        }
    }
}