How to read doc, docx file into .NET with C#.
I see you used the asp.net tag. You should not use the automation API (COM Interop) to run Microsoft Office products from ASP.NET or any other server application. The Office products are made to be run from the desktop - with a user interface. They don't work properly in a server scenario, and additionally, there are licensing issues.
Use Aspose.Words for .NET or some other such technology instead. They are designed to be used in a server environment.