Perception report sender

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.DirectoryServices;
using System.DirectoryServices.AccountManagement;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Mail;
using System.Net.Mime;
using System.Text;
using System.Windows.Forms;

namespace FileToEmailAddress
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.AllowDrop = true;
            this.DragEnter += new DragEventHandler(Form1_DragEnter);
            this.DragDrop += new DragEventHandler(Form1_DragDrop);
        }

        void Form1_DragEnter(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop)) e.Effect = DragDropEffects.Copy;
        }

        void Form1_DragDrop(object sender, DragEventArgs e)
        {
            if (!checkready())
            {
                MessageBox.Show("You cannot drag files onto this application until the text boxes have been filled in", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }
            if (checkusernameandpassword(txtUsername.Text, txtPassword.Text) == -1)
            {
                MessageBox.Show("The system cannot confirm your username and password. Are you on a University computer connected to the network?"
                    , "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }
            else if (checkusernameandpassword(txtUsername.Text, txtPassword.Text) == 0)
            {
                MessageBox.Show("Your username and password are not correct. These are required to send email."
                    , "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            string[] filesString = (string[])e.Data.GetData(DataFormats.FileDrop);

            int count = 0;

            foreach (string file in filesString)
            {
                string[] fileSplit = Path.GetFileName(file).Split('_');
                string username = "";
                try
                {
                     username = fileSplit[0];
                }
                catch
                {
                    MessageBox.Show("Failed find a username in the file " + file, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
                try
                {
                    SendMail(username + "@xxxx.ac.uk", file);
                    count++;
                }
                catch
                {
                    MessageBox.Show("Failed to send message to " + username + "@xxxx.ac.uk", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }

            MessageBox.Show("Emails have been sent to " + count.ToString() + " recipients", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
            this.Close();
        }

        private bool checkready()
        {
            if (txtBody.TextLength > 0 && txtEmail.TextLength > 0 && txtName.TextLength > 0 && txtPassword.TextLength > 0
                && txtSubject.TextLength > 0 && txtUsername.TextLength > 0)
            {
                return true;
            }
            else
            {
                return false;
            }
       }

        private void SendMail(string recipientEmail, string attachment)
        {
            string from = txtEmail.Text;
            string body = txtBody.Text ;
            string mailServerName = "smtp.xxxx.ac.uk";
            int mailServerPort = 25;
            string toAddress = recipientEmail;
            string subject = txtSubject.Text;

            string username = txtUsername.Text;
            string password = txtPassword.Text;

            SmtpClient mailClient = new SmtpClient(mailServerName,
                                                   mailServerPort);
            mailClient.Host = mailServerName;
            mailClient.Credentials = new NetworkCredential(username,
                                                           password);
            mailClient.EnableSsl = false;

            MailMessage message = new MailMessage(from, toAddress, subject, body);

            // Create  the file attachment for this e-mail message.
            Attachment data = new Attachment(attachment, MediaTypeNames.Application.Octet);
            // Add time stamp information for the file.
            ContentDisposition disposition = data.ContentDisposition;
            disposition.CreationDate = System.IO.File.GetCreationTime(attachment);
            disposition.ModificationDate = System.IO.File.GetLastWriteTime(attachment);
            disposition.ReadDate = System.IO.File.GetLastAccessTime(attachment);
            // Add the file attachment to this e-mail message.
            message.Attachments.Add(data);
            // Send
            mailClient.Send(message);
        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {
            txtEmail.Text = txtUsername.Text + "@xxxx.ac.uk";
            anyText_TextChanged(sender, e);
        }

        private void anyText_TextChanged(object sender, EventArgs e)
        {
            if (checkready())
            {
                lblDrop.Text = "Drop files here";
            }
            else
            {
                lblDrop.Text = "All boxes must first be filled in";
            }
        }

        /// <summary>
        /// Checks the username and password against AD
        /// </summary>
        /// <param name="username">AD username to compare to password</param>
        /// <param name="password">AD password to compare to username</param>
        /// <returns></returns>
        public int checkusernameandpassword(string username, string password)
        {
            // Presume that the username and password is wrong to start with
            int intToReturn = 0;
            try
            {
                // Use the existing domain that the computer is logged into
                PrincipalContext adContext = new PrincipalContext(ContextType.Domain);

                using (adContext)
                {
                    // Use the domain to check if the username and password go together
                    bool validPassword = adContext.ValidateCredentials(username.Trim(), password.Trim());

                    // If the password is correct
                    if (validPassword)
                    {
                        intToReturn = 1;
                    }
                    // If the password isn't correct
                    else
                    {
                        intToReturn = 0;
                    }
                }
            }
            // If we failed to connect to the domain then return a failed result
            catch
            {
                intToReturn = -1;
            }

            // Return the result to the main program
            return intToReturn;
        }
    }
}