2chBackAPI/DBchat.cs

using Npgsql;

namespace NeDvachAPI
{
    public class DBchat
    {
        // Obtain connection string information from the portal
        private static string Host = "postgres.vdk2ch.ru";
        private static string User = "postgres";
        private static string DBname = "postgres";
        private static string Password = "postgres";
        private static string Port = "5432";

        public static Post[] DbList()
        {
            // Build connection string using parameters from portal
            Post[] posts = new Post[10];
            int postCount = 0;
            string received = "";
            string connString =
                String.Format(
                    "Server={0}; User Id={1}; Database={2}; Port={3}; Password={4};SSLMode=Prefer",
                    Host,
                    User,
                    DBname,
                    Port,
                    Password);

            using (var conn = new NpgsqlConnection(connString))
            {


                conn.Open();


                using (var command = new NpgsqlCommand(@"
                SELECT * FROM 
                (SELECT post_id, substring(post,1,200) 
                FROM dvach 
                ORDER BY post_id 
                DESC limit 10) 
                subquery ORDER BY  post_id ASC", conn))
                {

                    var reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        //received +=(
                            //string.Format(
                                //"#{0}: {1}" + "\n",
                               // reader.GetInt32(0).ToString(),
                                //reader.GetString(1)
                                //)
                            //);
                        Post receivedPost = new()
                        {
                            Date = DateTime.Now,
                            Id = reader.GetInt32(0),
                            Text = reader.GetString(1)
                        };
                        posts[postCount] = receivedPost;
                        postCount++;
                    }
                    reader.Close();
                }
            }
            return posts;
        }

        public static void DbUpdate(string id, string text)
        {
            // Build connection string using parameters from portal
            string connString =
                String.Format(
                    "Server={0}; User Id={1}; Database={2}; Port={3}; Password={4};SSLMode=Prefer",
                    Host,
                    User,
                    DBname,
                    Port,
                    Password);

            using (var conn = new NpgsqlConnection(connString))
            {

                //Console.Out.WriteLine("Opening connection");
                conn.Open();

                using (var command = new NpgsqlCommand("UPDATE dvach " +
                    "SET post = @postText WHERE post_id = @ID", conn))
                {
                    command.Parameters.AddWithValue("ID", int.Parse(id));
                    command.Parameters.AddWithValue("postText", text);

                    int nRows = command.ExecuteNonQuery();
                    Console.Out.WriteLine(String.Format("Number of rows updated={0}", nRows));
                }
            }

            Console.WriteLine("Данные обновлены!");
            Console.ReadLine();
        }
        public static void SendPost(Post postToSend)
        {
            // Build connection string using parameters from portal
            //
            string connString =
                String.Format(
                    "Server={0}; User Id={1}; Database={2}; Port={3}; Password={4};SSLMode=Prefer",
                    Host,
                    User,
                    DBname,
                    Port,
                    Password);

            using (var conn = new NpgsqlConnection(connString))
            {

                Console.Out.WriteLine("Opening connection");
                conn.Open();

                using (var command = new NpgsqlCommand(@"
                INSERT INTO dvach " + @"(post_id, post) 
                VALUES (DEFAULT, @postText)", conn))
                {
                    command.Parameters.AddWithValue("postText", postToSend.Text);

                    int nRows = command.ExecuteNonQuery();
                    Console.Out.WriteLine(String.Format("Number of rows updated={0}", nRows));
                }
            }

            Console.WriteLine("С добавлением закончено");
        }
    }
}