public class TaskExample1 : Form {     public CancellationTokenSource m_cancellation = null;     private void buttonCancel_Click( object sender, EventArgs e )     {         if( m_cancellation != null )         {             if( m_cancellation.IsCancellationRequested == false )             {                 m_cancellation.Cancel();             }         }     }     private void AddOpacity( int nOpacity )     {         this.Opacity = nOpacity / 100.0;     }     private void buttonRun_Click( object sender, EventArgs e )     {         m_cancellation = new CancellationTokenSource();         UpdateOpacity cb = AddOpacity;         Task taskOpacity = Task.Factory.StartNew( () =>         {             int nOpacity = 0;             do             {                 ++ nOpacity;                 Invoke( cb, nOpacity );                 System.Threading.Thread.Sleep( 5 );             }while( nOpacity < 100 && m_cancellation.IsCancellationRequested == false );         } );         taskOpacity.ContinueWith( t =>         {             Invoke( cb, 100 );             m_cancellation.Dispose();             m_cancellation = null;         } );     } }