class Program
    {
        static void Main(string[] args)
        {
            SqlConnection conn = new SqlConnection();

            //1.手寫
            //string connStr = "server=.;database=db1;uid=sa;pwd=123";

            //2.SqlConnectionStringBuilder生成連線字串
            //SqlConnectionStringBuilder connStrBuilder = new SqlConnectionStringBuilder();
            
 
//connStrBuilder.DataSource = ".";//設定資料來源
            //connStrBuilder.InitialCatalog = "db1";//資料庫名
            //connStrBuilder.UserID = "sa";//賬號
            //connStrBuilder.Password = "123";//密碼
            //connStrBuilder.Pooling = false;//禁用連線池
            //string connStr = connStrBuilder.ConnectionString;

            
 
//3.讀取配置檔案裡的連線字串
            //3.1
            //string connStr = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;//讀取連線字串
            //3.2
            string connStr = ConfigurationManager.AppSettings["connStr"].ToString();


            //連線字串如果任何一個元素設定不正確，都不能正常開啟conn
            conn.ConnectionString = connStr;
            conn.Open();
            conn.Close();
        }
    }