Web Forms :: The Process Cannot Access The File 'c: Empmy.pdf' Because It Is Being Used By Another Process?

I've developed a popup email .aspx used on our intranet based web app that is auto generated with .pdf's attached. I'm developing with VS 2008 ASP.Net 3.5 C# and System.Net.Mail.MailMessage. I can create and send the email with no issues. The problem is with any attempt to open or delete the attachments I get the above error. The .pdf's a copied with the following code:

FileStream fsr = new FileStream(inFilename, FileMode.Open, FileAccess.Read, FileShare.Read);
BinaryReader reader = new BinaryReader(fsr);
byte[] bytes = new byte[fsr.Length];
reader.Read(bytes, 0, bytes.Length);
FileStream fsw = new FileStream(outFileName, FileMode.Create, FileAccess.Write, FileShare.Write);
BinaryWriter writer = new BinaryWriter(fsw);
writer.Write(bytes, 0, bytes.Length);
// clean up
writer.Flush();
writer.Close();
writer = null;
fsw.Close();
fsw.Dispose();
fsw = null;
reader.Close();
reader = null;
fsr.Close();
fsr.Dispose();
fsr = null;
Later after sending the email I:
mailMessage.Dispose();
mailMessage = null;
foreach (string fileName in attachments)
{
if (File.Exists(fileName))
File.Delete(fileName);
}

The error occurs at: the File.Delete(fileName);

how I can delete or reopen these files after sending the email?