这个调用怎么老是出错?

Question

DB_Conn.cs文件:
public class Conn_DB
    {
        //定义一个连接对象
        public SqlConnection Conn;
        //打开数据库连接
        public void DB_Open()
        {
            SqlConnection Conn = new SqlConnection("Server=.;Uid=sa;Pwd=;DataBase=NorthWind");
            Conn.Open();
        }
        //关闭数据库连接
        public void DB_Close()
        {
            Conn.Close();
        }
    }gridview.aspx.cs文件:
            Conn_DB CD = new Conn_DB();
            SqlDataAdapter sda = new SqlDataAdapter("Select * From Customers", CD.Conn);
            DataSet DS = new DataSet();
            sda.Fill(DS, "Customers");
            GridView1.DataSource = DS.Tables[0].DefaultView;
            GridView1.DataBind();
            CD.DB_Close();老是提示SelectCommand.Connection尚未初始化!!

Answer 1

DB_Open() 这个不是构造函数 又不调用

Answer 2

你为何要定义 public SqlConnection Conn；

Answer 3

public void DB_Open()
        {
             Conn = new SqlConnection("Server=.;Uid=sa;Pwd=;DataBase=NorthWind");
            Conn.Open();
        }

Answer 4

public SqlConnection  GetConn()
        {
            SqlConnection Conn = new SqlConnection("Server=.;Uid=sa;Pwd=;DataBase=NorthWind");
           return Conn;
           
        }
SqlDataAdapter sda = new SqlDataAdapter("Select * From Customers", CD.GetConn());

Answer 5

gridview.aspx.cs文件:
            Conn_DB CD = new Conn_DB();
            CD.DB_Open()            SqlDataAdapter sda = new SqlDataAdapter("Select * From Customers", CD.Conn);
            DataSet DS = new DataSet();
            sda.Fill(DS, "Customers");
            GridView1.DataSource = DS.Tables[0].DefaultView;
            GridView1.DataBind();
            CD.DB_Close();

Answer 6

还有你已经定义了
public SqlConnection Conn;//为公有成员变量
你还在
 public void DB_Open()
        {
            SqlConnection Conn = new SqlConnection("Server=.;Uid=sa;Pwd=;DataBase=NorthWind");//这里定义局部变量？
            Conn.Open();
        }