vb.net 如何在VB 2010中显示数据库连接状态
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How to display database connection status in VB 2010
提问by Geeth
I'm developing Point of sales system. and i want to display database connection status for the users. Im using MS Access 2013 database and Visual Studio 2010 (VB). I created module for this project as follows,
我正在开发销售点系统。我想为用户显示数据库连接状态。我使用 MS Access 2013 数据库和 Visual Studio 2010 (VB)。我为这个项目创建了如下模块，
Imports System.Data.OleDb
Module ModConVar
Public sql As String
Public cmd As OleDbCommand
Public dr As OleDbDataReader
Public conn As OleDbConnection
Public connStr As String = System.Environment.CurrentDirectory.ToString & "\NCS_POS_DB.accdb"
Public Sub ConnDB()
Try
conn = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & connStr & "")
conn.Open()
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
End Module
And I have a label named lblDBStatus in main MDI form, I tried with followin code, but it dosent work.
我在主 MDI 表单中有一个名为 lblDBStatus 的标签，我尝试使用以下代码，但它不起作用。
If conn.State = ConnectionState.Open Then
lblDBStatus.Text = "CONECTED"
End If
any suggestions please ??
请问有什么建议吗？？
回答by ?s??? ????
You're displaying "CONNECTED" only when the connection state is open. Otherwise your label will not show anything
CONNECTED仅当连接状态为打开时才显示“ ”。否则您的标签将不会显示任何内容
Try this and make sure that the connection is open:
试试这个并确保连接是打开的：
If conn.State = ConnectionState.Open Then
lblDBStatus.Text = "CONNECTED"
Else
lblDBStatus.Text = "DISCONNECTED"
End If
回答by Bj?rn-Roger Kringsj?
The OleDbConnectionexposes a StateChangedevent.
该OleDbConnection的暴露了StateChanged事件。
So you can track the state like this:
所以你可以像这样跟踪状态：
Public Sub ConnDB()
Using connection As New OleDbConnection("...")
AddHandler connection.StateChange, AddressOf Me.OnConnectionStateChange
Try
connection.Open()
'Do stuff..
Catch ex As Exception
Throw ex
Finally
RemoveHandler connection.StateChange, AddressOf Me.OnConnectionStateChange
End Try
End Using
End Sub
Private Sub OnConnectionStateChange(sender As Object, e As StateChangeEventArgs)
MessageBox.Show(e.CurrentState.ToString())
End Sub
