How to Block application with demo version

Try

If My.Computer.Network.IsAvailable = False Then

MessageBox.Show("Your internet is not available. please connect your internet cable or check any other issue.", "Black Hawkers", MessageBoxButtons.OK, MessageBoxIcon.Information)

Application.Exit()

Else

Dim ws As New WebClient

Dim str As String = ws.DownloadString("http://blocksys.com/Devil.txt")

If str = "blocking" Then

MessageBox.Show("This application has been blocked by administrator", "Application blocked", MessageBoxButtons.OK, MessageBoxIcon.Error)

Application.Exit()

End If

End If

 

I know about this code but its working not well

so please help me