ApplicationClass WordOper = new ApplicationClass();
String filePath = Server.MapPath("../Files/Book.doc");
Object file = filePath;
object nullobj = System.Reflection.Missing.Value;
Document doc = WordOper.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);
Document doc1 = WordOper.ActiveDocument;
string m_Content = doc1.Content.Text;
TextBox1.Text = m_Content;
doc.Close(ref nullobj, ref nullobj, ref nullobj);