using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
using Spire.Doc;

namespace WindowsFormsApp7
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            SaveFileDialog dlg = new SaveFileDialog();
            dlg.Filter = "PDF Documents|*.pdf|Word Documents|*.docx|Text Documents|*.txt";

            string fileName = string.Empty;

            if (dlg.ShowDialog() == DialogResult.OK)
            {
                fileName = dlg.FileName;

                switch (dlg.FilterIndex)
                {
                    case 1:
                        iTextSharp.text.Document document = new iTextSharp.text.Document();
                        PdfWriter.GetInstance(document, new FileStream(fileName, FileMode.Create));
                        document.Open();

                        Paragraph p1 = new Paragraph(richTextBox1.Text);
                        document.Add(p1);
                        document.Close();
                        break;

                    case 2:
                        Spire.Doc.Document doc = new Spire.Doc.Document();
                        Spire.Doc.Section section = doc.AddSection();

                        Spire.Doc.Documents.Paragraph paragraph = section.AddParagraph();
                        paragraph.AppendText(richTextBox1.Text);

                        doc.SaveToFile(fileName, FileFormat.Docx);
                        break;

                    case 3:
                        File.WriteAllText(fileName, richTextBox1.Text);
                        break;
                }
            }
        }
    }
}