谁帮我详细解释下C#的下面代码含义?

SqlConnection thisConnection = new SqlConnection(
"Server=(local);Integrated Security=True;" +
"Database=stu");
thisConnection.Open();

SqlCommand thisCommand = thisConnection.CreateCommand();

SqlConnection thisConnection = new SqlConnection("Server=(local);Integrated Security=True;" +"Database=stu");//获得一个Connection连接实例
thisConnection.Open();//用连接实例打开数据库连接

SqlCommand thisCommand = thisConnection.CreateCommand();//通过连接实例创建Command对象，该对象包含书库操作方法

//初始化数据库连接，传入连接词

SqlConnection thisConnection = new SqlConnection( "Server=(local);Integrated Security=True;" + "Database=stu");

//打开连接 thisConnection.Open();

//初始化SqlCommand用于执行SQL语句

SqlCommand thisCommand = thisConnection.CreateCommand();

建立SQL连接，并将SQL 命令绑定到该链接。

接下来就可以给 命令赋值SQL 语句，来执行返回记录结果了。