after email deleting attachment file, error "The process cannot access the file because it is being used by another process."

Question

I am doing an email form. Email has attachments and after attaching files email is sent. Next there is requirement to delete file from server. When I tried to get the file it gave me the subject error. I am even calling GC.Collect() before deleting the file but error is still there. My code for deleting file is:

 private void DeleteFiles(DataTable dt)
{
    GC.Collect();
    String[] sAttachments = new String[dt.Rows.Count];
    try
    {

        sAttachments = new String[dt.Rows.Count];
        for (Int32 J = 0; J < dt.Rows.Count; J++)
        {
            sAttachments[J] = dt.Rows[J]["AttachmentExt"].ToString().Trim();
            string workDir = Server.MapPath(".") + @"\upload\";
            if (File.Exists(workDir + sAttachments[J]))
                File.Delete(workDir + sAttachments[J]);                
        }
    }
    catch (Exception ex)
    {

    }

For attaching file to email my code is:

 oMess.Subject = sSubject; 
        string workDir = System.Web.HttpContext.Current.Server.MapPath(".") + @"\upload\";
        if (Attachments != null)
        {
            for (Int32 I = 0; I < Attachments.Length; I++)
            {
                oatt = new Attachment(workDir+ sAttachments[I]);
                oMess.Attachments.Add(oatt);
            }
        }
        oMess.IsBodyHtml = IsHtml;
        oMess.Body = sBody;
       SendMessageGmail(oMess);

Edit: My mail sending code is:

 private void SendMessageGmail(MailMessage message)        
    {
        SmtpClient client = new SmtpClient("smtp.gmail.com");
        client.EnableSsl = true;
        client.UseDefaultCredentials = false;
        NetworkCredential loginInfo = new NetworkCredential("myid", "mypassword");
        client.Credentials = loginInfo;
        client.Port = 587;
        client.Send(message);
    }

Plz guide and help. thanks

Answer 1

Use this one. It worked for me

client.Send(oMess);
oMess.Attachments.Dispose();

I tried this one but it didn`t work for me

client.Send(oMess);
oMess.Dispose();