sqlconnection 关闭时的 C# System.InvalidOperationException

如何解决sqlconnection 关闭时的 C# System.InvalidOperationException

system.invalidOperationException：超时已过期。
在从池中获取连接之前超时时间已过。 这可能是因为所有池连接都在使用中并且达到了最大池大小。

private void uploadDbButton_Click(object sender,EventArgs e) { Cursor.Current = Cursors.WaitCursor;

    countLabel.Text = autoid("Olvasasok","olvasas_szama");
 
        string query,itemVlaue = "";
       
        sqlCommand cmd;
        
        if(kiadas.Checked)
        {
            radio = "K";
        }
        else if (bevetelezes.Checked)
        {
            radio = "B";
        }

   


        if (inventoryList.Items.Count > 0)
        {
            for (int i = 0; i < inventoryList.Items.Count; i++)
            {
                connect = new sqlConnection(conStr);
                DateTime time = DateTime.Now;
                String format = "yyyy-MM-dd";
                DateTime ido = DateTime.Now;
                String forma = "HH:mm:ss";
             
            
                itemVlaue = inventoryList.Items[i].Text;
                query = "INSERT INTO Olvasasok (olvasas_szama,rfid_tag,datum,ido,irany)VALUES ('" + countLabel.Text +"','" + itemVlaue + "','" + DateTime.Now.ToString(format) +"','" + DateTime.Now.ToString(forma) + "','" + radio +"')";
                cmd = new sqlCommand(query,connect);

                

                if (connect.State == ConnectionState.Closed)
                {
                    connect.open();
                }


                cmd.ExecuteNonQuery();
            }

            connect.Close();
            functionCallStatusLabel.Text = "Feltöltés sikerült...";

        }
        else
        {
            MessageBox.Show("Csatlakozz rá egy olvasóra...");

        }
        inventoryList.Items.Clear();
        m_TagTable.Clear();
        m_TagTotalCount = 0;
        totalTagValueLabel.Text = "0(0)";
        this.uploadDbButton.Enabled = false;


    }

解决方法

潜在地，很多 SqlConnection 可以打开并且永不关闭：

if (inventoryList.Items.Count > 0)
{
    for (int i = 0; i < inventoryList.Items.Count; i++)
    {
        // For each loop,create new SqlConnection object
        connect = new SqlConnection(conStr);
        // Already true,because the connect is new SqlConnection object
        if (connect.State == ConnectionState.Closed)
            connect.Open();
        ...
    }
    //Close only the last SqlConnection
    connect.Close();
}

也许您可以尝试将 SqlConnection 封装在 using 中：

if (inventoryList.Items.Count > 0)
{
    // Create one SqlConnection
    using(var connect = new SqlConnection(conStr))
    {
        // Open one SqlConnection
        connect.Open();
        for (int i = 0; i < inventoryList.Items.Count; i++)
        {
            ...
        }
    }
    // End of using,the SqlConnection is automatically closed
}