title: Active form in a Windows application?
body: <p>I am developing a <a href="http://en.wikipedia.org/wiki/Windows_Forms" rel="nofollow noreferrer">Windows Forms</a> application.
  I have four forms which is inherited from Baseform in another project.
  In all four forms I am using a label to show some transaction count based on network status. I have implemented a thread which gets the active form of application and setting up the text. The code works fine if application screen is active. If I minimize and open any other application, I am getting an null error exception.</p>
  
  <p>How do I get the active form of an application?</p>
  
  <pre><code>Private Sub StartThread() 
      pollThread =New Thread(AddressOf PollfileStatus) 
      pollThread.IsBackground =True
      running =True
      pollThread.Start()
  End Sub
  
  Private Sub PollfileStatus() 
      While (running)
          Try
              For Each e As Control In Me.ActiveForm.Controls 
                  If (e.Name = "pbStatus") Then
                      e.Invoke(New SetTextCallback(AddressOf Settext), 
                          New Object() {e, 10}) 
                  End If
              Next
          Catch ex As Exception 
              Throw New ApplicationException(ex.Message) 
          End Try
          Thread.Sleep(6000)
      End While
  End Sub 
  </code></pre>