private void menuItemOpen_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFile = new OpenFileDialog();

            openFile.InitialDirectory = Application.ExecutablePath;
            openFile.Filter = "rtf files (*.rtf)|*.rtf|txt files (*.txt)|*.txt|All files (*.*)|*.*";
            openFile.FilterIndex = 1;
            openFile.RestoreDirectory = true;

            if (openFile.ShowDialog() == DialogResult.OK)
            {
                string fullName = openFile.FileName;
                string fileName = Path.GetFileName(fullName);

                if (FindDocument(fileName) != null)
                {
                    MessageBox.Show("The document: " + fileName + " has already opened!");
                    return;
                }

                FormAbapDoc abapDoc = new FormAbapDoc();
                abapDoc.Text = fileName;
                if (dockPanel.DocumentStyle == DocumentStyle.SystemMdi)
                {
                    abapDoc.MdiParent = this;
                    abapDoc.Show();
                }
                else
                    abapDoc.Show(dockPanel);
                try
                {
                    abapDoc.OpenFile(fullName);
                    // abapDoc.FileName = fullName;
                }
                catch (Exception exception)
                {
                    abapDoc.Close();
                    MessageBox.Show(exception.Message);
                }

            }
        }
        private FormAbapDoc CreateAbapDoc()
        {
            var abapDoc = new FormAbapDoc();

            return abapDoc;
        }