how to open excel file in document viewer in WPF.

<grid>
        <textblock margin="104,10,436,25" fontweight="Bold">Upload Document File</textblock>
        <textbox height="32" horizontalalignment="Left" margin="21,35,0,0" name="FileNameTextBox">
                 VerticalAlignment="Top" Width="181" Text="
" />
        <button content="Browse" horizontalalignment="Left" margin="227,35,0,0">
                Name="btnBrowse" Width="88" Click="btnBrowse_Click" Height="32" VerticalAlignment="Top"/>
        <button content="view" horizontalalignment="Left" margin="355,35,0,0">
                Name="btnView" Width="88" Click="btnView_Click" Height="32" VerticalAlignment="Top"/>
        <documentviewer name="DocView" margin="21,76,32,30" />        
    </button></button></textbox></grid>

string filename = "";
        string xpsFileName = "";
        string path = "";

   private void ViewDocumentViewer()
        {
            try
            {
                var excelApp = new Microsoft.Office.Interop.Excel.Application();
                excelApp.DisplayAlerts = false;
                excelApp.Visible = false;
                Microsoft.Office.Interop.Excel.Workbook excelWorkbook = excelApp.Workbooks.Open(path);
                ExportXPS(excelWorkbook);
                excelWorkbook.Close(false, null, null);
                excelApp.Quit();
                Marshal.ReleaseComObject(excelApp);
                excelApp = null;
            }
            catch
            { }
        }

        void ExportXPS(Microsoft.Office.Interop.Excel.Workbook excelWorkbook)
        {
            xpsFileName = (new DirectoryInfo(path)).FullName;
            xpsFileName = xpsFileName.Replace(new FileInfo(path).Extension, "") + ".xps";
            excelWorkbook.ExportAsFixedFormat(XlFixedFormatType.xlTypeXPS,
            Filename: xpsFileName,
            OpenAfterPublish: false);
        }

        void DisplayXPSFile()
        {
            XpsDocument xpsPackage = new XpsDocument(xpsFileName, FileAccess.Read, CompressionOption.NotCompressed);
            FixedDocumentSequence fixedDocumentSequence = xpsPackage.GetFixedDocumentSequence();
            DocView.Document = fixedDocumentSequence;
        }

        private void btnView_Click(object sender, RoutedEventArgs e)
        {
            ViewDocumentViewer();
            DisplayXPSFile();
        }

        private XpsDocument ConvertWordDocToXPSDoc(string wordDocName, string xpsDocName)
        {

            // Create a WordApplication and add Document to it

            Microsoft.Office.Interop.Word.Application

                wordApplication = new Microsoft.Office.Interop.Word.Application();

            wordApplication.Documents.Add(wordDocName);





            Document doc = wordApplication.ActiveDocument;

            // You must ensure you have Microsoft.Office.Interop.Word.Dll version 12.

            // Version 11 or previous versions do not have WdSaveFormat.wdFormatXPS option

            try
            {

                doc.SaveAs(xpsDocName, WdSaveFormat.wdFormatXPS);

                wordApplication.Quit();



                XpsDocument xpsDoc = new XpsDocument(xpsDocName, System.IO.FileAccess.Read);

                return xpsDoc;

            }

            catch (Exception exp)
            {

                string str = exp.Message;

            }

            return null;

        }

        private void BrowseFile()
        {
            Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();



            // Set filter for file extension and default file extension

            dlg.DefaultExt = ".doc";

            dlg.Filter = "Word documents (.doc)|*.docx";



            // Display OpenFileDialog by calling ShowDialog method

            Nullable<bool> result = dlg.ShowDialog();



            // Get the selected file name and display in a TextBox

            if (result == true)
            {

                if (dlg.FileName.Length > 0)
                {

                    FileNameTextBox.Text = dlg.FileName;

                    string newXPSDocumentName = String.Concat(System.IO.Path.GetDirectoryName(dlg.FileName), "\\",

                                   System.IO.Path.GetFileNameWithoutExtension(dlg.FileName), ".xps");



                    // Set DocumentViewer.Document to XPS document

                    DocView.Document =

                        ConvertWordDocToXPSDoc(dlg.FileName, newXPSDocumentName).GetFixedDocumentSequence();

                }

            }
        }

        private void btnBrowse_Click(object sender, RoutedEventArgs e)
        {

            string filePath = "";
            Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();
            dlg.DefaultExt = ".txt";
            dlg.Filter = "EXCEL Files (*.xls)|*.xlsx";
            Nullable<bool> result = dlg.ShowDialog();
            if (result == true)
            {
                filename = dlg.FileName;
                FileNameTextBox.Text = filename;
                filePath = System.IO.Path.Combine("C:\\Users\\m.kashif\\Desktop\\uploaded files\\");
            }
            SaveFileDialog _SD = new SaveFileDialog();
            _SD.Filter = "Text File (*.txt)|*.txt|Show All Files (*.*)|*.*";
            _SD.FileName = "Untitled";
            _SD.Title = "Save As";

            string directory = System.IO.Path.GetDirectoryName(Assembly.GetEntryAssembly().Location);
            //  filePath = System.IO.Path.Combine(filename);

            string name = System.IO.Path.GetFileName(filename);
            filePath = "C:\\Users\\m.kashif\\Desktop\\uploaded files\\" + name;
            if (!File.Exists(filePath))
            {
                string destinationFilename = System.IO.Path.Combine("C:\\Users\\m.kashif\\Desktop\\uploaded files\\", name);
                File.Copy(filename, destinationFilename);
                path = destinationFilename;
                MKSEmployee._value = path;

            }
            else
            {
                MessageBox.Show("File Already Exist");
                FileNameTextBox.Text = string.Empty;
            }
        }</bool></bool>