Mira si tienes agragada la referencia Microsoft.Office.Interop.Word.Application en tu proyecto he intenta con estas dos formas para ver si te funciona:
1.
Código Javascript
:
Ver originalMicrosoft.Office.Interop.Word.Application app = new Microsoft.Office.Interop.Word.Application();
app.Visible = true;
object visible = true;
object fileName = @"C:\temp\sample.doc";
object optional = System.Type.Missing;
Microsoft.Office.Interop.Word.Document doc = app.Documents.Open(ref fileName, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional, ref optional,ref optional,ref optional,ref optional,ref optional,ref optional,ref optional);
2.
Código Javascript
:
Ver originalstring fPath = @"c:/abc/doc/abc1.doc";
FileInfo myDoc = new FileInfo(fPath);
Response.Clear(); Response.ContentType = "Application/msword";
Response.AddHeader("content-disposition", "attachment;filename=" + myDoc.Name);
Response.AddHeader("Content-Length", myDoc.Length.ToString());
Response.ContentType = "application/octet-stream";
Response.WriteFile(myDoc.FullName);
Response.End();
Espero y te sirva.