C#

Gizz quoted his supplier:

You should only ever add/remove an event handler once in most applications. It is not designed by Microsoft to have event handlers added and removed continuously as a method to controlling these things.

Gizz continued to quote his supplier:

This is because an event handler is usually dealt with in another thread (or how else could it be generated for the application)

and adding/removing notifications to the other thread can easily be the subject of racetrack timing errors.

Reanalyse wrote:

returnstring.Replace(@absolutefile,@fname);

returnstring = returnstring.Replace(...)

public class HardFileStream : FileStream
{
  private bool hardPositionSet;

  public HardFileStream( string path )
    : base( path, FileMode.OpenOrCreate, FileAccess.ReadWrite ) {}

  public bool HasHardPositionSet
  {
    get
    {
      return hardPositionSet;
    }
  }

  // Sets the position of the file stream and prevents seeking to other positions.
  public void SetHardPosition( long pos )
  {
    base.Position = pos;
    hardPositionSet = true;
  }

  // Releases the hold on seeking.
  public void ReleaseHardPosition()
  {
    hardPositionSet = false;
  }

  public override long Position
  {
    get
    {
      return base.Position;
    }
    set
    {
      if( !hardPositionSet )
        base.Position = value;
    }
  }

  public override bool CanSeek
  {
    get
    {
      return !hardPositionSet;
    }
  }

  public override long Seek( long offset, SeekOrigin origin )
  {
    if( !hardPositionSet )
    {
      return base.Seek( offset, origin );
    }
    return 0;
  }
}

HardFileStream fs = new HardFileStream( "test.dat" );
Image img;
img = Image.FromFile( "image1.jpg" );
img.Save(fs,ImageFormat.Jpeg);
img.Dispose();

long p2 = fs.Position;
img = Image.FromFile( "image2.jpg" );
img.Save( fs, ImageFormat.Jpeg );
img.Dispose();

fs.Position=0; //set the stream position to the start of image1
pictureBox1.Image = Image.FromStream(fs);
fs.SetHardPosition( p2 ); //set the stream position to the start of image2
pictureBox2.Image = Image.FromStream(fs);
fs.ReleaseHardPosition();

"we must lose precision to make significant
      statements about complex systems."
              -deKorvin on uncertainty