我在论坛上寻找了解决这个问题的方法，但我找不到一个问题。点击按钮，我收到错误：
已经有一个与此Connection关联的打开DataReader，必须先关闭它。
因此，我尝试在使用它们之后关闭所有DataReader，我尝试使用CommandBehavior，但它们都没有用。我尝试使用using(MysqlCommand...)但是没有用。我能做什么？最奇怪的是代码工作正常，但按下每个按钮后，我再次收到该错误。有什么想法吗？
请不要将问题标记为副本，我知道这里存在问题，但我猜错了答案。
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
using System.Drawing.Text;
namespace simulator
{
public partial class Simulare : Form
{
public int corect = 0, incorect = 0;
Timer timer;
static string dataA = "SELECT DISTINCT * FROM questions order by rand() limit 1";
public int r1;
public int r2;
public int r3;
public Simulare()
{
InitializeComponent();
this.FormClosing += Form1_FormClosing;
label1.Text = TimeSpan.FromMinutes(30).ToString("mm\\:ss");
label10.Text = corect.ToString();
label12.Text = incorect.ToString();
//FormBorderStyle = FormBorderStyle.None;
WindowState = FormWindowState.Maximized;
}
private void simulare_Load(object sender, EventArgs e)
{
var startTime = DateTime.Now;
timer = new Timer() { Interval = 1000 };
timer.Tick += (obj, args) =>
{
TimeSpan ts = TimeSpan.FromMinutes(30) - (DateTime.Now - startTime);
label1.Text = ts.ToString("mm\\:ss");
if (ts.Minutes == 00 && ts.Seconds == 00)
{
timer.Stop();
MessageBox.Show("Timpul a expirat. Ai picat!");
MySqlCommand upd = new MySqlCommand("select totalno from accounts where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection());
try
{
MySqlDataReader upad = upd.ExecuteReader();
while (upad.Read())
{
int totalnu = (int)upad["totalno"];
totalnu++;
using (MySqlCommand update = new MySqlCommand("UPDATE accounts SET totalno=@totalnu where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection()))
{
update.Parameters.AddWithValue("@totalnu", totalnu);
int rows = update.ExecuteNonQuery();
}
}
upad.Close();
}
catch (Exception ex2)
{
MessageBox.Show(ex2.Message);
}
}
};
timer.Start();
select();
}
private void select()
{
using (ConnConfig.getConnection())
{
MySqlCommand cmd = new MySqlCommand(dataA, ConnConfig.getConnection());
cmd.CommandType = CommandType.Text;
MySqlDataReader rdra = cmd.ExecuteReader(CommandBehavior.CloseConnection);
try
{
while (rdra.Read())
{
label2.Text = rdra["question"].ToString();
label3.Text = rdra["answer1"].ToString();
label4.Text = rdra["answer2"].ToString();
label5.Text = rdra["answer3"].ToString();
r1 = (int)rdra["option1"];
r2 = (int)rdra["option2"];
r3 = (int)rdra["option3"];
}
rdra.Close();
}
catch (InvalidOperationException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
ConnConfig.closeConn();
}
}
}
private void button1_Click(object sender, EventArgs e)
{
int result1 = checkBox1.CheckState == CheckState.Checked ? 1 : 0;
int result2 = checkBox2.CheckState == CheckState.Checked ? 1 : 0;
int result3 = checkBox3.CheckState == CheckState.Checked ? 1 : 0;
using(ConnConfig.getConnection())
{
MySqlCommand cmd = new MySqlCommand(dataA, ConnConfig.getConnection());
cmd.CommandType = CommandType.Text;
MySqlDataReader rdr = cmd.ExecuteReader();
try
{
while (rdr.Read())
{
if (checkBox1.Checked == false && checkBox2.Checked == false && checkBox3.Checked == false)
{
MessageBox.Show("Bifati minim o casuta!");
return;
}
else
{
if ((result1 == r1) && (result2 == r2) && (result3 == r3))
{
corect++;
label10.Text = corect.ToString();
checkBox1.Checked = false;
checkBox2.Checked = false;
checkBox3.Checked = false;
select();
}
else
{
incorect++;
label12.Text = incorect.ToString();
checkBox1.Checked = false;
checkBox2.Checked = false;
checkBox3.Checked = false;
select();
}
if (corect + incorect == 26)
{
int totalalll;
timer.Stop();
button1.Enabled = false;
MySqlCommand upd = new MySqlCommand("select * from accounts where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection());
MySqlDataReader upad = upd.ExecuteReader();
while (upad.Read())
{
totalalll = (int)upad["totalall"];
totalalll++;
using (MySqlCommand update = new MySqlCommand("UPDATE accounts SET totalall=@totalalll where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection()))
{
update.Parameters.AddWithValue("@totalalll", totalalll);
Int32 rows = update.ExecuteNonQuery();
}
}
upad.Close();
}
if (corect == 26)
{
MySqlCommand upd = new MySqlCommand("select totalyes from accounts where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection());
MySqlDataReader upad = upd.ExecuteReader();
while (upad.Read())
{
int totalda = (Int32)upad["totalyes"];
totalda++;
using (MySqlCommand update = new MySqlCommand("UPDATE accounts SET totalyes=@totalda where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection()))
{
update.Parameters.AddWithValue("@totalda", totalda);
int rows = update.ExecuteNonQuery();
}
}
upad.Close();
MessageBox.Show("Bravos");
}
else
{
MySqlCommand upd = new MySqlCommand("select totalno from accounts where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection());
MySqlDataReader upad = upd.ExecuteReader();
while (upad.Read())
{
int totalnu = (int)upad["totalno"];
totalnu++;
using (MySqlCommand update = new MySqlCommand("UPDATE accounts SET totalno=@totalnu where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection()))
{
update.Parameters.AddWithValue("@totalnu", totalnu);
int rows = update.ExecuteNonQuery();
}
}
upad.Close();
MessageBox.Show("Mai invata!");
}
}
}
rdr.Close();
}
catch (MySqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
ConnConfig.closeConn();
}
}
}
private void Form1_FormClosing(Object sender, FormClosingEventArgs e)
{
if (e.CloseReason == CloseReason.WindowsShutDown) return;
if (this.DialogResult == DialogResult.Cancel)
{
e.Cancel = false;
timer.Stop();
}
}
private void button2_Click(object sender, EventArgs e)
{
this.Close();
}
}
}
class ConnConfig
{
private static string conn = "string connection";
public static MySqlConnection connect;
private ConnConfig()
{
}
public static MySqlConnection getConnection()
{
if(connect !=null){
return connect;
}
else
try{
connect = new MySqlConnection(conn);
connect.Open();
return connect;
}
catch(MySqlException e){
throw new Exception("Cannot connect",e);
}
}
public static void closeConn()
{
connect.Close();
}
public static void openConn()
{
connect.Open();
}
}
答案 0 :(得分：1)
您的异常的根本原因是您在迭代先前查询的结果时正在执行其他查询。 如果对嵌套查询使用相同的连接，则不应像嵌套查询一样嵌入查询。
答案 1 :(得分：1)
您正在使用reader从SQLCommand upd获取数据。
然后你正在读价值。
之后您正在使用另一个SqlCommand＆＃39;更新＆＃39;更新结果..
即使使用两个不同的SQLCommands，也使用相同的连接。那就是问题所在。为第二个SQLCommand使用sperate连接，您的问题将得到解决。
试试这个。
行后
MessageBox.Show("Timpul a expirat. Ai picat!");
添加喜欢
MessageBox.Show("Timpul a expirat. Ai picat!");
MySqlConnection conn1 = ConnConfig.getConnection();
MySqlConnection conn2 = new MySqlConnection();
conn2.ConnectionString = conn1.ConnectionString;
conn2.Open();
然后在行
MySqlCommand upd = new MySqlCommand("select totalno from accounts where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection());
改变如
MySqlCommand upd = new MySqlCommand("select totalno from accounts where username = '" + Index.textBox1.Text + "'", conn1);
并在行
using (MySqlCommand update = new MySqlCommand("UPDATE accounts SET totalno=@totalnu where username = '" + Index.textBox1.Text + "'", ConnConfig.getConnection()))
改变如
using (MySqlCommand update = new MySqlCommand("UPDATE accounts SET totalno=@totalnu where username = '" + Index.textBox1.Text + "'", conn2))
答案 2 :(得分：1)
更改getConnection功能
public static MySqlConnection getConnection()
{
MySqlConnection connect = null;
try
{
connect = new MySqlConnection(connect);
connect.Open();
return connect;
}
catch (MySqlException e)
{
throw new Exception("Cannot connect", e);
}
}
让所有其他代码原样