Automating an MS Word Mail Merge using C#

Below is a sniper of code from an application I'm writing in C#. I have added the Microsoft Office Word 11.0 Object Library and the TEMPLATE_FILENAME constant has a valid filename. However the code hangs on the statement



           //Open Microsoft Word
            Microsoft.Office.Interop.Word.ApplicationClass wordapp = new Microsoft.Office.Interop.Word.ApplicationClass();
            wordapp.Visible = false;

            object filename = TEMPLATE_FILENAME;
            object objTrue = true;
            object objFalse = false;
            object objMiss = Type.Missing;
            Microsoft.Office.Interop.Word.Document myMergeDocument;

            myMergeDocument = wordapp.Documents.Open(ref filename, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss, ref objMiss);
            myMergeDocument.Select();

           
            //Microsoft.Office.Interop.Word.MailMerge mailMerge = myMergeDocument.MailMerge;

            // ON THE LINE BELOW: "COMException was unhandled." and "requested object is not available"
            myMergeDocument.MailMerge.Destination = Microsoft.Office.Interop.Word.WdMailMergeDestination.wdSendToNewDocument;
            myMergeDocument.MailMerge.SuppressBlankLines = true;
            myMergeDocument.MailMerge.DataSource.FirstRecord = (int)Microsoft.Office.Interop.Word.WdMailMergeDefaultRecord.wdDefaultFirstRecord;
            myMergeDocument.MailMerge.DataSource.LastRecord = (int)Microsoft.Office.Interop.Word.WdMailMergeDefaultRecord.wdDefaultLastRecord;
            myMergeDocument.MailMerge.Execute(ref objFalse);
            //myMergeDocument.Close();
                       
            wordapp.Visible = true;
            wordapp.ShowMe();
            return;


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I have a word document that is set up with a mail merge source already and I just want to make it open and perform the merge. The merge source is a text file. The Open command doesn't seem to work correctly because the mail merge toolbar is disabled. Someone please help!!!


(I know how to use try catch blocks - i'm interested in fixing the problem...not just handling it gracely)