连接必须有效并打开 VB.Net [英] Connection must be valid and open VB.Net

问题描述

我想将我的 MySQL 连接到我的 VB.net.我只使用登录表单.我已经给出了代码，但代码给了我这个错误信息:Connection must be valid and open

I want to connect my MySQL to my VB.net. I am only using Login Form. I have given the code but the code gives me this error message: Connection must be valid and open

这是我的代码:

Imports MySql.Data.MySqlClient
Public Class Login 
    Dim MysqlConn As MySqlConnection
    Dim Command As MySqlCommand

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        MysqlConn = New MySqlConnection
        MysqlConn.ConnectionString ="server=db4free.net;port=3306;userid=exd****;password=****;database=exd****"
        Dim Reader As MySqlDataReader

    Try
        MysqlConn.Open()
        Dim Query As String
        Query = "select * from member where Username='" & UsernameTxt.Text & "' and Password='" & PasswordTxt.Text & "' "
        Command = New MySqlCommand
        Reader = Command.ExecuteReader
        Dim count As Integer
        count = 0

        While Reader.Read
            count = count + 1
        End While

        If count = 1 Then
            MessageBox.Show("Correct !")
        ElseIf count > 1 Then
            MessageBox.Show("Duplicate !")
        Else
            MessageBox.Show("Not Correct !")
        End If

        MysqlConn.Close()

    Catch ex As Exception
         MsgBox(ex.Message)
    Finally
        MysqlConn.Dispose()
    End Try

    End Sub

End Class

谁能帮我解决这个问题?谢谢.

Can anyone help me to fix that? Thanks.

推荐答案

您在任何时候都不会将您的 MysqlConn 或 Query 与您的 Command 相关联> 在尝试对其调用 ExecuteReader 之前.因此，它当时没有有效的连接.

At no point do you associate your MysqlConn nor Query to your Command before trying to call ExecuteReader on it. As such, it doesn't have a valid connection at that time.

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