c#連接sql資料庫

public static string sqlserver = ConfigurationManager.ConnectionStrings["MyDB"].ConnectionString;

using (SqlConn = new SqlConnection(sqlserver))
        {
            SqlConn.Open();//連接到SQL資料庫

            sql = "select "; //查詢用語法

            using (SqlCmd = new SqlCommand(sql, SqlConn))
            {
                using (Reader = SqlCmd.ExecuteReader())
                {
                  Reader.Read();//要先Read才有資料

                  int test = Reader.GetInt32(0); //後面GET要跟撈出來的資料同個型態

                  =============下面這邊不用先Reader.Read(); 就能將資料給GridView==========

                    GridView1.DataSource = Reader;//設定GridView的資料來源

                    GridView1.DataBind();
                ============================================================
                }
            }
       }

using (SqlConn = new SqlConnection(sqlserver))
        {
            SqlConn.Open();

            using (SqlCmd = SqlConn.CreateCommand())
        {

             SqlCmd.CommandText = "INSERT INTO" //新增、更改資料、刪除資料都用這種寫

                SqlCmd.ExecuteNonQuery(); //執行SQL語法

        }

    }