Mysql 已经有一个打开的DataReader与此连接关联，必须先关闭该连接

我有个错误

已存在与此连接关联的打开的DataReader，必须先关闭该连接

这是我的密码。 你能帮我吗？？？ 多谢各位

    MySqlConnection = New MySqlConnection
    MySqlConnection.ConnectionString = "server = localhost; port=3307; user id = root; password = 1234; database = mcs;"
    Dim READER As MySqlDataReader


    If cmbxyear.Text = "NURSERY" Then


        MySqlConnection.Open()
        Dim query As String
        query = " select student_no from mcs.fullpayment_nursery where student_no = '" & txtstudent_no.Text & "'"
        Dim Command As New MySqlCommand(query, MySqlConnection)
        READER = Command.ExecuteReader
        If query = txtstudent_no.Text Then

            MessageBox.Show("YOU DON'T HAVE REMAINING BALANCE")
            MySqlConnection.Close()


        Else

            Dim query1 As String
            query1 = " select student_balance from mcs.installmentpayment_nursery where student_no = '" & txtstudent_no.Text & "'"
            Dim Command1 As New MySqlCommand(query1, MySqlConnection)
            READER = Command.ExecuteReader
            READER.Read()
            txtstudentbalance.Text = READER(0)


            MessageBox.Show("Student Balance Generated")
            MySqlConnection.Close()


        End If

---

错误消息本身就说明了这一点。无法在已打开的连接上打开第二个数据读取器。也就是说，你的代码没有意义。您需要重新评估您试图实现的目标，并编写合理的代码来实现它。您的

If

语句（

If query=txtstuden\u no.Text Then

）将永远不会为真，因此代码将永远不会被执行。此外，您的代码容易受到sql注入攻击。