ME3Explorer.PCCRepack.buttonDecompressPCC_Click C# (CSharp) Method

        private void buttonDecompressPCC_Click(object sender, EventArgs e)
        {
            if (openPccDialog.ShowDialog() == DialogResult.OK)
            {
                string fileName = openPccDialog.FileName;
                string backupFile = fileName + ".bak";
                if (File.Exists(fileName))
                {
                    try
                    {
                        DialogResult dialogResult = MessageBox.Show("Do you want to make a backup file?", "Make Backup", MessageBoxButtons.YesNo);
                        if (dialogResult == DialogResult.Yes)
                        {
                            File.Copy(fileName, backupFile);
                        }

                        MemoryStream m;
                        using (FileStream fs = new FileStream(fileName, FileMode.Open))
                        {
                            m = CompressionHelper.DecompressME3(fs);
                        }
                        File.WriteAllBytes(fileName, m.ToArray());

                        MessageBox.Show("File " + Path.GetFileName(fileName) + " was successfully decompressed.", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    }
                    catch (Exception exc)
                    {
                        MessageBox.Show("An error occurred while compressing " + Path.GetFileName(fileName) + ":\n" + exc.Message, "Exception Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        //recovering backup file
                        if (File.Exists(backupFile))
                        {
                            File.Delete(fileName);
                            File.Move(backupFile, fileName);
                        }
                    }
                }
            }
        }