与数据库连接从中读取数据的几种常见的形式

 1 我们一般执行插入，删除等这些对数据库的操作会影响到数据表的行数，可用以下代码

 string strConn = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
        using (SqlConnection conn = new SqlConnection())
        {
            conn.ConnectionString = strConn;
            conn.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "insert into TestTable values(name,age)";
            int row = cmd.ExecuteNonQuery();       
        
        }

2.返回查询结果的两种 

  string strConn = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
        using (SqlConnection conn = new SqlConnection())
        {
            conn.ConnectionString = strConn;
            conn.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "select *from TestTable";
            SqlDataReader dr = cmd.ExecuteReader();
            DataTable dt = new DataTable();
            dt.Load(dr);
            dr.Close();        
        }

 string strConn = ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
        using (SqlConnection conn = new SqlConnection())
        {
            conn.ConnectionString = strConn;
            conn.Open();
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = "select *from TestTable";
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = conn;
            DataSet ds =new  DataSet();
            da.Fill(ds, "data");
           // 这里ds.Tables["data"];里就是查询结果
      
        }