Question

我一直在

InvalidOperationException：ExecuteReader需要一个开放且可用的连接。连接的当前状态已关闭。]

这是因为我的连接已关闭。我的连接字符串有什么问题？为什么不打开它。

    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

另外，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无法收集资源。

HTH

Answer 2

设置连接字符串后，需要调用conn.Open（）。

编辑：Woops，Markust用40秒击败我，xD

Answer 3

更改您的连接字符串，如下所示......

conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;" +
            @"Data source= c:\\inetpub\\wwwroot\\cm485a2\\rreAccesscm485a2.mdb";

*note: '\\' instead of '\'

无法连接到远程MS Access数据库

3 个答案: