连接必须有效并打开 VB.Net
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Connection must be valid and open VB.Net
提问by Donquixote Adiyatma
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
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
This is my code:
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
Can anyone help me to fix that? Thanks.
谁能帮我解决这个问题？谢谢。
回答by Daniel Waghorn
To associate your Queryand Commandwith the connection you need to do this:
要将您的Query和Command与连接相关联，您需要执行以下操作：
Command = New MySqlCommand(Query, MysqlConn)
You can then perform operations to retrieve the data you need.
然后您可以执行操作来检索您需要的数据。
回答by Rowland Shaw
At no point do you associate your MysqlConnnor Queryto your Commandbefore trying to call ExecuteReaderon it. As such, it doesn't have a valid connection at that time.
在尝试调用它之前，您MysqlConn绝不会将您的或 Query与您的关联。因此，它当时没有有效的连接。CommandExecuteReader
回答by Ger.-
Query = "select * from member where Username='" & UsernameTxt.Text & "' and Password='" & PasswordTxt.Text & "' ", nombredelaconexion
Query = "select * from member where Username='" & UsernameTxt.Text & "' and Password='" & PasswordTxt.Text & "' ", nombredelaconexion
