public List<Category> FindAll()
        {
            List<Category> Categories = new List<Category>();
            string query = "SELECT * FROM Category";

            using (SqlConnection db = new SqlConnection(CONN_STR))
            {
                if (db.State != System.Data.ConnectionState.Open)
                {
                    db.Open();
                }

                using (SqlCommand cmd = db.CreateCommand())
                {
                    cmd.CommandText = query;

                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            Category c = new Category();
                            c.CategoryID = reader.GetInt32(reader.GetOrdinal("CategoryID"));
                            c.CategoryName = reader.GetString(reader.GetOrdinal("CategoryName"));
                            Categories.Add(c);
                        }
                    }
                }
            }
            return Categories;
        }
        public Category Save(Category category)
        {
            string query = @"INSERT INTO Category (
                                CategoryID, 
                                CategoryName
                            ) VALUES (
                                @CategoryID,
                                @CategoryName
                            )";

            using (SqlConnection db = new SqlConnection(CONN_STR))
            {
                if (db.State != System.Data.ConnectionState.Open)
                {
                    db.Open();
                }

                using (SqlCommand cmd = db.CreateCommand())
                {
                    cmd.CommandText = query;
                    cmd.Parameters.AddWithValue("CategoryID", category.CategoryID);
                    cmd.Parameters.AddWithValue("CategoryName", category.CategoryName);
                    cmd.ExecuteNonQuery();

                    cmd.CommandText = "SELECT @@Identity";
                    category.CategoryID = (int)(decimal)cmd.ExecuteScalar();
                }
            }

            return category;
        }
        public void Delete(Category category)
        {
            string query = "DELETE FROM Category";

            using (SqlConnection db = new SqlConnection(CONN_STR))
            {
                if (db.State != System.Data.ConnectionState.Open)
                {
                    db.Open();
                }

                using (SqlCommand cmd = db.CreateCommand())
                {
                    cmd.CommandText = query;
                    cmd.ExecuteNonQuery();
                }
            }
        }