c# - Interop.Word Documents.Open is null

Question

I am trying to open .docx file and convert to PDF using Interop.Word.Application. It works as console application but If I use the same in my web application it doesn't work. I tried to see the permissions on the folder. I gave 'Network Service' with full control, but still I get object reference not set at word.Documents.Open. Could you please let me know what could be the problem? I am stuck with this error. Please let me know. I appreciate any suggestions. Thank you.

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

    object oMissing = System.Reflection.Missing.Value;

    word.Visible = false;
    word.ScreenUpdating = false;
    string fileName = @"c:OUTPUTest.docx");
    Document doc = word.Documents.Open(filename, ref oMissing,
            ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
            ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
            ref oMissing, ref oMissing, ref oMissing, ref oMissing);
        doc.Activate();

Answer 1

If you are still looking for the answer I have found it just a moment ago for my project.

Open DCOM Config Settings:

1. Start -> dcomcnfg.exe
2. Computer
3. Local Computer
4. Config DCOM
5. Search for Microsoft Word 97-2003 Documents -> Properties

Tab Identity, change from Launching User to Interactive User