错误关闭在C＃中访问数据库

Question

 private void FoodList_Load(object sender, EventArgs e) { 

     try { 
       **Connections.con.Open();** 

       OleDbCommand cmd = new OleDbCommand(); 
       cmd.Connection = Connections.con; 
       string foodcon = "SELECT ID, FoodName FROM FoodList"; 
       cmd.CommandText = foodcon; 
       OleDbDataReader reader = cmd.ExecuteReader(); 

       while (reader.Read()) 
       { 
        listBox1.Items.Add(reader["FoodName"].ToString()); 
       } 


     } 
     catch (Exception err) 
     { 
      MessageBox.Show("Error " + err); 

     } 
     **Connections.con.Close();** 

连接的问题已经关闭的代码下面的连接，但是当我登录有一个错误，告诉我该连接仍然是开放的？有什么建议么？

Answer 1

如上所述，创建命令对象时应该创建连接对象。你应该这样做：

using (var connection = new OleDbConnection("...")) 
using (var command = new OleDbCommand("...", connection)) 
{ 
    connection.Open(); 

    using (var reader = command.ExecuteReader()) 
    { 
     // ... 
    } 
}