Why we use .Deny in VB.NET?

Question

Hi, Every-one few days ago i was check some VB.NET example's over the different website's in one example I saw .Deny(). The example are:

Imports System.Security.Principal
Imports System.Security.Permissions
Imports System.IO
Imports System.Diagnostics

public class MainClass
   Shared Sub Main()
        Dim oRp As New RegistryPermission(Security.Permissions.PermissionState.Unrestricted)
        oRp.Deny()
        Dim objLog As New EventLog
        Dim objLogEntryType As EventLogEntryType
        Try
            Throw (New EntryPointNotFoundException)
        Catch objA As System.EntryPointNotFoundException
            Try
                If Not System.Diagnostics.EventLog.SourceExists("Example") Then
                    System.Diagnostics.EventLog.CreateEventSource("Example", "System")
                End If
                objLog.Source = "Example"
                objLog.Log = "System"
                objLogEntryType = EventLogEntryType.Information
                objLog.WriteEntry("Error: " & objA.Message, objLogEntryType)
            Catch objB As System.Exception
                Console.WriteLine(objB.Message)
            End Try
        End Try
   End Sub
End Class

Sonebody plz guide me why we use .Deny and why this program give error when I was compile this program?