===============<box>==========================
  Public Class myFile
     Public Sub New( p As String , b As Boolean )
      …
     End Sub
     Public Function Read() As String
      …
     End Sub
     Public Sub Write(s As String)
      …
     End Sub
  End Class
===============<end>====================



===============<box>===========================
   Module T
     Public Sub Main()
         Dim f As New myFile(“c:\test\sys.txt”)
         Dim s As String = f.Read()
          f.Write(“資料已被更動”)
        …
     End Sub
   End Module
===================<end>============================



=================<box>================
Option Explicit On 
Imports System.IO
Imports System.Security
Imports System.Security.Permissions 
Public Class myFile
 Public Sub Write()
    Dim pa As New FileIOPermissionAccess()
    Dim p As New FileIOPermission(pa.Write, "c:\test\test.txt")
    p.Demand()
    Dim s As FileStream = Nothing        
   s = New FileStream("C:\test\test.txt", FileMode.OpenOrCreate, FileAccess.Write)
   Dim w As New StreamWriter(s)
   w.Write("Test String")
   w.Close()
   s.Close()
 End Sub
End Class
=============<end>==============



=============<box>==============
Imports System.Security
Imports myFile

  Class A
    Public Shared Sub Main()
         Try 
             Dim f As New myFile()
             f.Write()
             System.Console.WriteLine("寫入Test.txt成功!")
          Catch ex As SecurityException
             System.Console.WriteLine("存取Test.txt被拒!")
          Catch 
             System.Console.WriteLine("程式執行失敗!")
          End Try
    End Sub
  End Class
=============<end>==============



=============<box>==============
Option Explicit On
Imports System.Security.Permissions
Imports System.Security
Imports Microsoft.VisualBasic
Public Class myFile
    Public Sub Write()
        Dim pa As New FileIOPermissionAccess()
        Dim p As New FileIOPermission(pa.Write, "c:\test\test.txt")
        p.Assert()
　    Dim s As FileStream = Nothing        
   s = New FileStream("C:\test\test.txt", FileMode.OpenOrCreate, FileAccess.Write)
    Dim w As New StreamWriter(s)
    w.Write("Test String")
    w.Close()
    s.Close()
 End Sub
End Class
=============<end>==============



=============<box>==============
Option Explicit On
Imports System.Security.Permissions
Imports System.Security
Imports Microsoft.VisualBasic
Public Class myFile
    Public Sub Write()
        Dim pa As New FileIOPermissionAccess()
        Dim p As New FileIOPermission(pa.Write, "c:\test\test.txt")
        p.Deny()
      Dim s As FileStream = Nothing        
   s = New FileStream("C:\test\test.txt", FileMode.OpenOrCreate, FileAccess.Write)
     Dim w As New StreamWriter(s)
     w.Write("Test String")
     w.Close()
     s.Close()
 End Sub
End Class
=============<end>==============



=============<box>==============
Option Explicit On 
Imports System.Security.Permissions
Imports System.Security
Imports Microsoft.VisualBasic

<Assembly: PermissionSet(SecurityAction.RequestOptional, unrestricted:=False)> 

Public Class myFile
    Public Sub Write()
      Dim s As FileStream = Nothing        
   s = New FileStream("C:\test\test.txt", FileMode.OpenOrCreate, FileAccess.Write)
     Dim w As New StreamWriter(s)
     w.Write("Test String")
     w.Close()
     s.Close()
 End Sub
End Class
=============<end>==============



=============<box>==============
Option Explicit On 
Imports System.Security.Permissions
Imports System.Security
Imports Microsoft.VisualBasic

<Assembly: PermissionSet(SecurityAction.RequestOptional, unrestricted:=False)> 
<Assembly: FileIOPermission(SecurityAction.RequestMinimum, ALL:="C:\Test.txt")> 

Public Class myFile
    Public Sub Write()
      Dim s As FileStream = Nothing        
   s = New FileStream("C:\test\test.txt", FileMode.OpenOrCreate, FileAccess.Write)
     Dim w As New StreamWriter(s)
     w.Write("Test String")
     w.Close()
     s.Close()
 End Sub
End Class
=============<end>==============