Question

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消息：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

任何人都可以帮我解决这个问题吗？感谢。

Answer 1

要将Query和Command与您需要的连接相关联：

Command = New MySqlCommand(Query, MysqlConn)

然后，您可以执行操作以检索所需的数据。

Answer 2

在尝试呼叫MysqlConn之前，您没有将Query和Command与ExecuteReader相关联。因此，它当时没有有效的连接。

Answer 3

Query =“select * from member where Username ='”＆amp; UsernameTxt.Text＆amp; “'和密码='”＆amp; PasswordTxt.Text＆amp; “'”， nombredelaconexion

连接必须有效并打开VB.Net

3 个答案: