Microsoft.Office.Interop.Word.ApplicationClass wordApp = new ApplicationClass();
 
            object file = textBox1.Text;
            object nullobj = System.Reflection.Missing.Value;
 
            Microsoft.Office.Interop.Word.Document doc = wordApp.Documents.Open(ref file, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj, ref nullobj);                              
 
            doc.ActiveWindow.Selection.WholeStory();
            doc.ActiveWindow.Selection.Copy();
            IDataObject data = Clipboard.GetDataObject();
 
            richTextBox1.Text = data.GetData(DataFormats.Text).ToString();
 
            doc.Close(ref file, ref nullobj,ref nullobj);