如何访问DataConnection UWP中的表数据

Question

所以我连接数据库（也测试了连接）工作得很好

那么如何从中获取数据？

在App.cs中，我创建了一个连接字符串

        public string connectionString = "Server = DESKTOP-Q42NBTE; Database = FirstDataBase; Trusted_Connection = true";
    public string ConnectionString
    {
        get => connectionString; set => connectionString = value;
    }

还创建了一个包含所有数据的类 类BooksData：

    public class BooksData
{
    public string Title { get; set; }
    public string Description { get; set; }
    public string ImageFile { get; set; }
    public int Price { get; set; }
    public int PublisherID { get; set; }
    public int AuthorID { get; set; }
    public int BookID { get; set; }
}

和沟通的方法

    public ObservableCollection<BooksData> GetBooks(string connectionString)
    {
        const string GetBooksQuery = "select * from Books";
        var books = new ObservableCollection<BooksData>();
        try
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                conn.Open();
                if (conn.State == System.Data.ConnectionState.Open)
                {
                    using (SqlCommand cmd = conn.CreateCommand())
                    {
                        cmd.CommandText = GetBooksQuery;
                        using (SqlDataReader reader = cmd.ExecuteReader())
                        {
                            while (reader.Read())
                            {
                                var book = new BooksData();
                                book.Title = reader.GetString(0);
                                book.Price = reader.GetInt32(1);
                                book.ImageFile = reader.GetString(2);
                                book.PublisherID = reader.GetInt32(3);
                                book.AuthorID = reader.GetInt32(4);
                                book.BookID = reader.GetInt32(5);
                            }
                        }
                    }
                }
            }
            return books;
        }
        catch (Exception eSql)
        {
            Debug.WriteLine("Exception: " + eSql.Message);
        }
        return null;
    }

但没有任何工作

这是我的数据库信息