BuecherwurmAPI/Models/ItemModel.cs

using System;
using System.Collections.Generic;
using BuecherwurmAPI.Models;
using Microsoft.Data.Sqlite;
using Microsoft.VisualBasic.CompilerServices;

namespace BuecherwurmAPI.Models
{
    public interface IItem
    {
        
    }

    internal class ItemModel : IItem
    {
        private SqliteConnection _dbConnection;
        
        public ItemModel()
        {
            var connectionBuilder = new SqliteConnectionStringBuilder {DataSource = "LongWormMemory.db"};
            _dbConnection = new SqliteConnection(connectionBuilder.ConnectionString);
            _dbConnection.Open();
        }

        public bool IdExits(string table, long id)
        {
            using (var command = _dbConnection.CreateCommand())
            {
                command.Parameters.Add(new SqliteParameter("@Id", SqliteType.Integer)).Value = id;
                
                // Certain parts of the query can't be filled with variables for security reasons.
                switch (table)
                {
                    case Tables.Table.Items: 
                        command.CommandText = @"SELECT EXISTS(SELECT 0 FROM Items WHERE Id = @Id)";
                        break;
                }
                
                var dr = command.ExecuteReader();
                
                long result = 0;
                while (dr.Read())
                {
                    result = (long) dr[0];
                }
                return result != 0;
            }
        }

        public IEnumerable<Item> GetAllItems()
        {
            var items = new List<Item>();

            // using automatically disposes the command after completion
            using (var command = _dbConnection.CreateCommand())
            {
                command.CommandText = "SELECT * FROM Items";
                var dataReader = command.ExecuteReader();
                
                while (dataReader.Read())
                {
                    items.Add(new Item
                    {
                        ItemId = (long) dataReader["ItemId"],
                        BookId = (long) dataReader["BookId"]
                    });
                }
            }
            return items;
        }

        public Item GetItemById(long itemId)
        {
            using (var command = _dbConnection.CreateCommand())
            {
                command.Parameters.Add(new SqliteParameter("@itemId", itemId));
                command.CommandText = "SELECT * FROM Items WHERE ItemId = @itemId";
                var dataReader = command.ExecuteReader();

                while (dataReader.Read())
                {
                    var item = new Item
                    {
                        ItemId = (long) dataReader["ItemId"],
                        BookId = (long) dataReader["BookId"]
                    };
                    return item;
                }
            }
            return null;
        }
        public Item NewItem(ItemPost itemPost)
        {
            using (var command = _dbConnection.CreateCommand())
            {
                //hier soll jetz der NewItem Command folgen. ein POST mit EingabeInfo {id} = "BookId"
                command.CommandText = "INSERT INTO Items (BookId) VALUES (@bookId)";
                command.CommandType = System.Data.CommandType.Text;
                command.Parameters.Add(new SqliteParameter("@bookId", itemPost.BookId));
                command.ExecuteNonQuery();
                command.CommandText = "select last_insert_rowid()";
                var LastRowId64 = (long)command.ExecuteScalar();
                var item = new Item{
                    ItemId = LastRowId64,
                    BookId = itemPost.BookId
                };
                return item;             
            }
        }

        public void DeleteItem(long itemId)
        {
            using (var command = _dbConnection.CreateCommand())
            {
                command.CommandText = "DELETE FROM Items WHERE ItemId = @itemId";
                command.Parameters.Add(new SqliteParameter("@itemId", itemId));
                command.ExecuteNonQuery();                
            }
        }
    }
}