Question

我要做的是保持MySQL连接从Window1（LoginWindow）打开到Window2（DBAA）。这样在第二个窗口中我就可以读取和插入数据。当我尝试插入数据时，我得到了＃34; Host不允许连接到这个MySQL服务器＆＃34;

Imports MySql.Data.MySqlClient

Public Class LoginWindow
    Dim MysqlConn As MySqlConnection
    Public Sub Button_Click(sender As Object, e As RoutedEventArgs)
        MysqlConn = New MySqlConnection()

        MysqlConn.ConnectionString = "server=" & server.Text & ";" _
        & "user id=" & username.Text & ";" _
        & "password=" & password.Password & ";" _
        & "database=" & database.Text & ";"
        Try
            MysqlConn.Open()
            MessageBox.Show("Connection to Database has been opened.")
        Catch myerror As MySqlException
            MessageBox.Show("Cannot connect to database: " & myerror.Message)
        Finally
            MysqlConn.Dispose()
        End Try
        Dim DBAA As DBAA = New DBAA
        DBAA.Show()
        Me.Hide()
    End Sub

   //Non Applicable Code

End Class

这是打开的第二个窗口（DBAA）。

Imports MySql.Data.MySqlClient
Imports System.Data.Sql

Public Class DBAA
    Dim con As New MySqlConnection
    Dim result As Integer
    Dim cmd As New MySqlCommand

    Private Sub insert01_Click_1(sender As Object, e As RoutedEventArgs) Handles insert01.Click
        Try
            con.Open()

            With cmd
                .Connection = con
                .CommandText = "INSERT INTO `test`.`data` (`value1`) " & _
                                "VALUES ('" & data01.Text & "');"
                result = cmd.ExecuteNonQuery
                If result = 0 Then
                    MsgBox("Success!")
                End If
            End With
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
        con.Close()
    End Sub
End Class

Answer 1

在您的第二个代码中，您定义了连接，但遗漏了您的连接信息。您需要提供连接详细信息。你打电话给.Open连接，但它没有你的连接信息。

也不要保持开放，根本不是好的做法。你关闭它的第一个代码很好，但是你的第二个代码遗漏了一些细节。

编辑...

如果你想传递连接，你可以在构造函数中这样做......

确保你在第二节课中有这个......

 Private Property connection As MySqlConnection 
 Public Sub New(ByVal con as MySqlConnection)
    connection = con
 End Sub

现在您可以使用＆＃39;连接＆＃39;你想要的地方......

然后你将当前连接作为第二个类的参数传递...

    Dim DBAA As DBAA = New DBAA(MysqlConn)

在Visual Basic中保持MySQL连接打开

1 个答案: