c# - 无法连接到远程 MS Access 数据库

Question

我不断得到一个

InvalidOperationException:ExecuteReader 需要一个打开且可用的连接。连接的当前状态是关闭的。]

这是因为我的连接已关闭。我的连接字符串有什么问题？为什么打不开。

    protected void Page_Load(object sender, EventArgs e)
    {
        // Declaration section

        //OleDbConnection objDBConn;
        OleDbCommand    objCmd;
        OleDbDataReader objDR;

        //create connection object
        System.Data.OleDb.OleDbConnection conn = new
          System.Data.OleDb.OleDbConnection();

        // Modify the connection string and include any
        // additional required properties for your database.
        conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;" +
            @"Data source= c:\inetpub\wwwroot\cm485a2\rreAccesscm485a2.mdb";

          // Create OleDbCommand object with SQL to execute
            objCmd = new OleDbCommand("SELECT * " +
                            "  FROM customers " +
                            " ORDER BY cust_id", conn);

            // Create a DataReader and execute the command
            objDR = objCmd.ExecuteReader();

            // Copy results from DataReader to DataGrid object
            GridView1.DataSource = objDR;
            GridView1.DataBind();


            //close all objects
            conn.Close();
            conn.Dispose();

    }

Answer 1

您需要先打开连接。

http://msdn.microsoft.com/en-us/library/system.data.oledb.oledbconnection.open.aspx

此外，我会使用 using 来避免资源泄漏，如下所示:

using (var connection = new OleDbConnection())
{
  connection.Open();
  using (var command = new OleDbCommand("connectionString"))
  {
     //Do my stuff.
  }
}

这种方式更容易让 GC 不收集资源。

HTH