how to run a function/sub after loading the form window in VB? - vb.net

Question

I have a function that gets User ID from USB badge reader, used to log in an application.
when I run the app, the log in window does not appear until I swipe the tag.
I need to know if it`s possible to load the windows, then to start running the function that gets the data from the USB.
Thanks :)
Private Sub SerialPort1_DataReceived()
'Threading.Thread.SpinWait(1000)
OpenPort()
If SerialPort1.IsOpen() Then
byteEnd = SerialPort1.NewLine.ToCharArray
'read entire string until .Newline
readBuffer = SerialPort1.ReadLine()
readBuffer = readBuffer.Remove(0, 1)
readBuffer = readBuffer.Remove(8, 1)
WWIDTextBox.AppendText(readBuffer)
End If
End Sub
Private Sub Form1_Activated(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles MyBase.Activated
SerialPort1_DataReceived()
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'SerialPort1_DataReceived()
End Sub

Answer 1

The problem is that you are calling the ReadLine method, which is a blocking (synchronous) method. In other words, when you call it, the method does not return the value until it has the value to return. Because of that, it stops execution on the current thread until a complete line is read (when the badge is swiped). Since you are on the UI thread when you call it, it will lock up the UI until the badge is swiped.
Instead of calling your SerialPort1_DataReceived method from the UI thread, you can do the work from a different thread. The easiest way to do that is to drag a BackgroundWorker component onto your form in the designer. Then you can add code like this:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
OpenPort()
If SerialPort1.IsOpen() Then
byteEnd = SerialPort1.NewLine.ToCharArray
Dim readBuffer As String = SerialPort1.ReadLine()
readBuffer = readBuffer.Remove(0, 1)
readBuffer = readBuffer.Remove(8, 1)
e.Result = readBuffer
End If
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
WWIDTextBox.AppendText(CStr(e.Result))
End Sub

Answer 2

Working on VS2013, I came across the same issue, I needed to to a datagridview refresh (colors in the gridrows). This worked for me.
Sub MyForm_VisibleChanged(sender As Object, e As EventArgs) Handles Me.VisibleChanged
If Me.Visible Then
'do action...
End If
End Sub

Answer 3

Try Form Activated Event
Private Sub Form1_Activated(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles MyBase.Activated
'Call your function here
End Sub
It call the function After the Form Loads...

Answer 4

Private Sub loadCombo()
Dim sqlconn As New OleDb.OleDbConnection
Dim connString As String
connString = ""
Dim access As String
access = "select slno from atable"
Dim DataTab As New DataTable
Dim DataAdap As New OleDbDataAdapter(access, connString)
DataAdap.Fill(DataTab)
ComboBox1.DataSource = DataTab
ComboBox1.DisplayMember = "slno"
End Sub