Open file function

OpenFileDialog opendialogfile = new OpenFileDialog();
            opendialogfile.Filter = "Lua File (*.lua)|*.lua|Text File (*.txt)|*.txt";
            opendialogfile.FilterIndex = 2;
            opendialogfile.RestoreDirectory = true;
            if (opendialogfile.ShowDialog() != DialogResult.OK)
                return;
            try
            {
                fastColoredTextBox1.Text = "";
                System.IO.Stream stream;
                if ((stream = opendialogfile.OpenFile()) == null)
                    return;
                using (stream)
                    this.fastColoredTextBox1.Text = System.IO.File.ReadAllText(opendialogfile.FileName);
            }
            catch(Exception ex)
            {
                int num = (int)MessageBox.Show("An unexpected error has occured", "OOF!", MessageBoxButtons.OK, MessageBoxIcon.Information);

            }