Imports System.Threading
Imports System.Security.Permissions

<SecurityPermission(SecurityAction.Demand, Flags:=SecurityPermissionFlag.ControlThread)> _
Friend Class MyUtility
    <SecurityPermission(SecurityAction.Demand, Flags:=SecurityPermissionFlag.ControlThread)> _
    Public Sub PerformTask() 
        ' Code that does not have thread affinity goes here.
        '
        Thread.BeginThreadAffinity()
        '
        ' Code that has thread affinity goes here.
        '
        Thread.EndThreadAffinity()
        '
        ' More code that does not have thread affinity.
    End Sub 'PerformTask
End Class 'MyUtility 

using System.Threading;
using System.Security.Permissions;

[SecurityPermission(SecurityAction.Demand, Flags=SecurityPermissionFlag.ControlThread)]
public class MyUtility
{
    [SecurityPermission(SecurityAction.Demand, Flags=SecurityPermissionFlag.ControlThread)]
    public void PerformTask()
    {
        // Code that does not have thread affinity goes here.
        //
        Thread.BeginThreadAffinity();
        //
        // Code that has thread affinity goes here.
        //
        Thread.EndThreadAffinity();
        //
        // More code that does not have thread affinity.
    }
}

using namespace System::Threading;
using namespace System::Security::Permissions;

public ref class MyUtility
{
public:
   [SecurityPermissionAttribute(SecurityAction::Demand, ControlThread=true)]
   void PerformTask()
   {
      // Code that does not have thread affinity goes here.
      //
      Thread::BeginThreadAffinity();
      //
      // Code that has thread affinity goes here.
      //
      Thread::EndThreadAffinity();
      //
      // More code that does not have thread affinity.
   }
};