Question

我故意在txtbxemail.text中输入了错误的输入后，按下更新按钮，然后显示我创建的消息框。然后我更正了txtbxemail.text中的textinut并再次按下更新按钮。

然后它显示＆＃34;连接已经打开＆＃34;。

需要帮助和解决方案的详细说明。

我的代码：

private void button2_Click(object sender, EventArgs e)
    {
        if (MyMessageBox.ShowMessage("You are about to update an important record!", "ARE YOU SURE", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
        {
            MemoryStream ms = new MemoryStream();
            pictureBox1.Image.Save(ms, pictureBox1.Image.RawFormat);
            byte[] img = ms.ToArray();

            MemoryStream mss = new MemoryStream();
            pictureBox1.Image.Save(mss, pictureBox2.Image.RawFormat);
            byte[] imgg = mss.ToArray();

            MySqlCommand cmnd = new MySqlCommand("update rfidnew.rfidemployees set RFIDnum=@rfidnum,firstname=@fn,lastname=@ln,department=@dep,position=@posi,emailadd=@eadd,cellphone=@cp,licenseno=@licnse,platenumber=@pnumb,employeeimage=@eimage,vehicleimage=@vimage where id = @ID", myConn);

            cmnd.Parameters.Add("@ID", MySqlDbType.Int32).Value = txtbxid.Text;
            cmnd.Parameters.Add("@rfidnum", MySqlDbType.VarChar).Value = txtbxrfid.Text;
            cmnd.Parameters.Add("@fn", MySqlDbType.VarChar).Value = txtbxfn.Text;
            cmnd.Parameters.Add("@ln", MySqlDbType.VarChar).Value = txtbxln.Text;
            cmnd.Parameters.Add("@dep", MySqlDbType.VarChar).Value = txtbxdep.Text;
            cmnd.Parameters.Add("@posi", MySqlDbType.VarChar).Value = cmboboxpos.Text;
            cmnd.Parameters.Add("@eadd", MySqlDbType.VarChar).Value = txtbxemail.Text;
            cmnd.Parameters.Add("@cp", MySqlDbType.VarChar).Value = txtbxcp.Text;
            cmnd.Parameters.Add("@licnse", MySqlDbType.VarChar).Value = txtbxlic.Text;
            cmnd.Parameters.Add("@pnumb", MySqlDbType.VarChar).Value = txtbxplate.Text;
            cmnd.Parameters.Add("@eimage", MySqlDbType.Blob).Value = img;
            cmnd.Parameters.Add("@vimage", MySqlDbType.Blob).Value = imgg;
            MySqlDataReader myrdr;


            Regex rx = new Regex("\\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~=]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9]*[a-z0-9])?)\\Z");

            try
            {
                myConn.Open();

                if (!rx.IsMatch(txtbxemail.Text))
                {
                    MyMessageBox.ShowMessage("Invalid format in Email Add field", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    myConn.Close();
                    txtbxemail.Clear();
                    txtbxemail.Focus();
                    auto_load_table();

                }
                else
                {
                    myrdr = cmnd.ExecuteReader();

                    ExecMyQuery(cmnd, "You are trying to update a record");

                    auto_load_table();

                    View_all_data disvid = new View_all_data();
                    this.Dispose();
                    disvid.Show();

                    while (myrdr.Read())
                    {

                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

            myConn.Close();

        }


    }

Answer 1

完成数据库操作后应关闭连接。在您的情况下，您应该使用MySqlConnection块创建using的新实例，然后打开并关闭连接。

using(var myConn = new MySqlConnection("yourConnectionString"))
{
    try
    {  
        myConn.Open();
        if (!rx.IsMatch(txtbxemail.Text))
        {
            MyMessageBox.ShowMessage("Invalid format in Email Add field", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Information);
            myConn.Close();
            txtbxemail.Clear();
            txtbxemail.Focus();
            auto_load_table();
        }
        else
        {
            myrdr = cmnd.ExecuteReader();

            ExecMyQuery(cmnd, "You are trying to update a record");

            auto_load_table();

            View_all_data disvid = new View_all_data();
            this.Dispose();
            disvid.Show();

            while (myrdr.Read())
            {

            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
    myConn.Close();
}

Visual Studio 2015 C＃MYSQL-＆＃34;连接已经打开＆＃34;

1 个答案: