VB.net Cross-form Cross-thread form call? - vb.net

Question

I am working on a project which requires a separate form which is running a server thread to access and change another forms control location. I know how to call a control from another thread running on the same form but I'm not sure how to do it on a separate form and thread.

Answer 1

Here's a simple example...
Define the event in your server form, and raise it when appropriate:
Public Class frmServer
Public Event NewPosition(ByVal pt As Point)
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
' ... in response to something (probably not a button click!) ...
Dim x As Integer = 250
Dim y As Integer = 100
RaiseEvent NewPosition(New Point(x, y))
End Sub
End Class
In your main form, subscribe to that event when you create an instance of the server form. This can be done with the AddHandler statement and the AddressOf keyword. Then do the normal Invoke pattern to make sure it runs in the correct UI thread:
Public Class frmMain
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim server As New frmServer
AddHandler server.NewPosition, AddressOf server_NewPosition
server.Show()
End Sub
Private Delegate Sub dlgNewPosition(ByVal pt As Point)
Private Sub server_NewPosition(pt As Point)
If Me.InvokeRequired Then
Me.Invoke(New dlgNewPosition(AddressOf server_NewPosition), New Object() {pt})
Else
Me.Location = pt
End If
End Sub
End Class