Convert document file to HTML, PDF, RTF, XPS

//First you need to add the references of office file to your project
Step 1:Add reference of Office files
reference dll files name: Microsoft.Office.Interop.Word.dll, Microsoft.Vbe.Interop.dll, office.dll

//You have to create a new form in your project
Step 2:Create a new form

//Add the controls to the form
Step 3:Add the controls
See the attached snapshot for GUI of the form

//Write this code on the different control of the forms
Step 4:Write code on form.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Microsoft.Office.Interop.Word;
using System.IO;
using System.Diagnostics;

object format;//define it as globally at form level
Step 5:Write code on Source Button click
//Source means from which location(path) you are choosing a file
private void ButtonSource_Click(object sender, EventArgs e)
        {
            OpenFileDialog dialog = new OpenFileDialog();
            dialog.Filter = "Document files (*.doc)|*.doc|Document files (*.docx)|*.docx";
            dialog.InitialDirectory = "C:\\";
            dialog.Title = "Select a document file";
            if (dialog.ShowDialog() == DialogResult.OK)
            {
                TextBoxSource.Text = dialog.FileName;
            }
        }

Step 6:Write code on Destination Button click
//Destination means at which location(path) you want the converted file.
private void ButtonDestination_Click(object sender, EventArgs e)
        {
            using (FolderBrowserDialog fdialog = new FolderBrowserDialog())
            {
                if (DialogResult.OK == fdialog.ShowDialog())
                {
                    TextBoxDestination.Text = fdialog.SelectedPath;
                }
            }
        }
Step 7:Write code on Convert Button Click
private void ButtonConvert_Click(object sender, EventArgs e)
        {
            string existpath = TextBoxDestination.Text + "\\" + TextBoxFileName.Text + "." + CBCnvrttype.Text;
            if (File.Exists(existpath))
            {
                MessageBox.Show("File name already exists." + Environment.NewLine + "Please give a different name.","Error",MessageBoxButtons.OK,MessageBoxIcon.Error);
                TextBoxFileName.Focus();
                TextBoxFileName.SelectAll();
            }
            else
            {
                if (TextBoxSource.Text == "")
                {
                    MessageBox.Show("Please specify the source.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    ButtonSource_Click(ButtonSource, null);
                }
                else if (TextBoxDestination.Text == "")
                {
                    MessageBox.Show("Please specify the destination.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    ButtonDestination_Click(ButtonDestination, null);
                }
                else if (TextBoxFileName.Text == "")
                {
                    MessageBox.Show("Please specify the target file name.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    TextBoxFileName.Focus();
                }
                else
                {
                    try
                    {
                        Microsoft.Office.Interop.Word.Application newApp = new Microsoft.Office.Interop.Word.Application();

                        // specifying the Source & Target file names
                        object Source = TextBoxSource.Text;
                        object Target = TextBoxDestination.Text + "\\" + TextBoxFileName.Text + "." + CBCnvrttype.Text;

                        // Use for the parameter whose type are not known or  
                        // say Missing
                        object Unknown = Type.Missing;

                        // Source document open here
                        // Additional Parameters are not known so that are  
                        // set as a missing type
                        newApp.Documents.Open(ref Source, ref Unknown,
                             ref Unknown, ref Unknown, ref Unknown,
                             ref Unknown, ref Unknown, ref Unknown,
                             ref Unknown, ref Unknown, ref Unknown,
                             ref Unknown, ref Unknown, ref Unknown,
                             ref Unknown, ref Unknown);

                        // Specifying the format in which you want the output file
                        if (CBCnvrttype.Text == "HTML")
                        {
                            format = WdSaveFormat.wdFormatHTML;
                        }
                        else if (CBCnvrttype.Text == "PDF")
                        {
                            format = WdSaveFormat.wdFormatPDF;
                        }
                        else if (CBCnvrttype.Text == "RTF")
                        {
                            format = WdSaveFormat.wdFormatRTF;
                        }
                        else if (CBCnvrttype.Text == "XPS")
                        {
                            format = WdSaveFormat.wdFormatXPS;
                        }

                        //Changing the format of the document
                        newApp.ActiveDocument.SaveAs(ref Target, ref format,
                                ref Unknown, ref Unknown, ref Unknown,
                                ref Unknown, ref Unknown, ref Unknown,
                                ref Unknown, ref Unknown, ref Unknown,
                                ref Unknown, ref Unknown, ref Unknown,
                                ref Unknown, ref Unknown);

                        // for closing the application
                        newApp.Quit(ref Unknown, ref Unknown, ref Unknown);
                        MessageBox.Show("File converted successfully to" + " " + "'" + TextBoxFileName.Text + "." + CBCnvrttype.Text + "'" + Environment.NewLine + "at location" + " :" + " " + "'" + TextBoxDestination.Text + "'", "Conversion successfull", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        string convertedfilelocation = TextBoxDestination.Text + "\\" + TextBoxFileName.Text + "." + CBCnvrttype.Text;
                        DialogResult ans = MessageBox.Show("Do you want to convert another file?","File Converter",MessageBoxButtons.YesNo,MessageBoxIcon.Question);
                        if (ans == DialogResult.Yes)
                        {
                            TextBoxSource.Clear();
                            TextBoxDestination.Clear();
                            TextBoxFileName.Clear();
                            CBCnvrttype.SelectedItem = null;
                            ButtonSource.Focus();
                        }
                        else
                        {
                            string selectexistfile = "/select," + convertedfilelocation;
                            Process.Start("explorer.exe", selectexistfile);
                        }
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.Message.ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    }
                }
            }
        }