Problem in reading a symbols using C#

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C#3.5

I am trying to read a integration symbols and some other using C#. I have a .doc file . i am reading like ∫,∑. I don't have it in C# variable. I am developing a Question Paper Generation of Chemistry.Then what do i do? i will have to save this value into sql server database also.Code is below-

public void ReadMsWord()
{
   // variable to store file path
   string filePath = null;
   // open dialog box to select file 
   OpenFileDialog file = new OpenFileDialog();
   // dilog box title name
   file.Title = "Word File";
   // set initial directory of computer system
   file.InitialDirectory = @"C:\Users\shri\Desktop\EXTRA\question\TnA\demo_swarit.doc";
   // set restore directory 
   file.RestoreDirectory = true;

   // execute if block when dialog result box click ok button
   if (file.ShowDialog() == DialogResult.OK)
   {
       // store selected file path
       filePath = file.FileName.ToString();
   }

   try
   {
      // create word application
     Microsoft.Office.Interop.Word.Application word = new Microsoft.Office.Interop.Word.ApplicationClass();
     // create object of missing value
     object miss = System.Reflection.Missing.Value;
     // create object of selected file path 
     object path = filePath;
     // set file path mode 
     object readOnly = false;
     // open document                 
     Microsoft.Office.Interop.Word.Document docs = word.Documents.Open(ref path, ref miss, ref readOnly, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss);

     // select whole data from active window document
     docs.ActiveWindow.Selection.WholeStory();

     // handover the data to cllipboard 
     docs.ActiveWindow.Selection.Copy();

     // clipboard create reference of idataobject interface which transfer the data
     IDataObject data = Clipboard.GetDataObject();

     //set data into richtextbox control in text format
     richTextBox1.Text = data.GetData(DataFormats.Text).ToString();

     // read bitmap image from clipboard with help of iddataobject interface
     Image img = (Image)data.GetData(DataFormats.Bitmap);

     // close the document 
     docs.Close(ref miss, ref miss, ref miss);

    }
    catch (Exception ex) { MessageBox.Show(ex.ToString()); }
}