Zimogorov_Arseniy_OrdersManager/IssueBookForm.cs

using Npgsql;
using System;
using System.Configuration;
using System.Data;
using System.Windows.Forms;

namespace WindowsFormsApp4
{
    public partial class IssueBookForm : Form
    {
        private readonly string connStr = ConfigurationManager.ConnectionStrings["PostgreSQL"].ConnectionString;

        public IssueBookForm()
        {
            InitializeComponent();
        }

        private void IssueBookForm_Load(object sender, EventArgs e)
        {
            LoadLibraryName();
            LoadReaders();
        }

        private void LoadLibraryName()
        {
            string query = "SELECT name FROM libraries WHERE id = @libId";
            using (var conn = new NpgsqlConnection(connStr))
            using (var cmd = new NpgsqlCommand(query, conn))
            {
                cmd.Parameters.AddWithValue("libId", Session.LibraryId);
                conn.Open();
                var result = cmd.ExecuteScalar();
                labelLibraryName.Text = result != null ? "Библиотека: " + result.ToString() : "Библиотека: Неизвестно";
            }
        }

        private void LoadReaders()
        {
            string query = @"
                SELECT id, name || ' ' || lastname AS fullname 
                FROM users 
                WHERE library_id = @libId AND role_name = 'reader'
                ORDER BY lastname";
            DataTable dt = new DataTable();
            using (var conn = new NpgsqlConnection(connStr))
            using (var cmd = new NpgsqlCommand(query, conn))
            {
                cmd.Parameters.AddWithValue("libId", Session.LibraryId);
                conn.Open();
                using (var adapter = new NpgsqlDataAdapter(cmd))
                {
                    adapter.Fill(dt);
                }
            }
            comboBoxReader.DisplayMember = "fullname";
            comboBoxReader.ValueMember = "id";
            comboBoxReader.DataSource = dt;
            comboBoxReader.SelectedIndex = -1;
        }

        private void comboBoxReader_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBoxReader.SelectedValue == null) return;
            LoadAvailableBooks();
        }

        private void LoadAvailableBooks()
        {
            string query = @"
               SELECT 
    be.isbn,
    b.title || ' (инв. ' || be.isbn || ')' AS book_display
FROM book_exemplar be
JOIN book b ON be.book_id = b.id
WHERE be.status = 'available'
  AND be.library_id = @libId
ORDER BY b.title";
            DataTable dt = new DataTable();
            using (var conn = new NpgsqlConnection(connStr))
            using (var cmd = new NpgsqlCommand(query, conn))
            {
                cmd.Parameters.AddWithValue("libId", Session.LibraryId);
                conn.Open();
                using (var adapter = new NpgsqlDataAdapter(cmd))
                {
                    adapter.Fill(dt);
                }
            }
            comboBoxBook.DisplayMember = "book_display";
            comboBoxBook.ValueMember = "isbn";
            comboBoxBook.DataSource = dt;
            comboBoxBook.SelectedIndex = -1;
        }

        private void buttonIssue_Click(object sender, EventArgs e)
        {
            if (comboBoxReader.SelectedValue == null)
            {
                MessageBox.Show("Выберите читателя", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                return;
            }
            if (comboBoxBook.SelectedValue == null)
            {
                MessageBox.Show("Выберите книгу", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                return;
            }

            int readerId = Convert.ToInt32(comboBoxReader.SelectedValue);
            int isbn = Convert.ToInt32(comboBoxBook.SelectedValue); 

            try
            {
                using (var conn = new NpgsqlConnection(connStr))
                {
                    conn.Open();
                    string sql = "SELECT issue_book(@readerId, @employeeId, @isbn, @dueDays)";
                    using (var cmd = new NpgsqlCommand(sql, conn))
                    {
                        cmd.Parameters.AddWithValue("readerId", readerId);
                        cmd.Parameters.AddWithValue("employeeId", Session.UserId);
                        cmd.Parameters.AddWithValue("isbn", isbn);
                        cmd.Parameters.AddWithValue("dueDays", 14);
                        object result = cmd.ExecuteScalar();
                        if (result == null || result == DBNull.Value)
                        {
                            MessageBox.Show("Функция не вернула номер заказа", "Ошибка");
                            return;
                        }
                        int orderId = Convert.ToInt32(result);
                        MessageBox.Show($"Книга выдана! № заказа: {orderId}", "Успех", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        LoadAvailableBooks();
                    }
                }
            }
            catch (PostgresException ex)
            {
                MessageBox.Show($"Ошибка БД: {ex.MessageText}", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            catch (Exception ex)
            {
                MessageBox.Show($"Ошибка: {ex.Message}", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
    }
}