gistfile1.txt

using System;
using System.Collections.Generic;
using System.IO;
using Microsoft.Office.Interop.Word;

class Program
{
    static void Main(string[] args)
    {
        List<string> path = new List<string>(args);
        string filePath = string.Join(" ", path.ToArray());
        string folderPath = Path.GetDirectoryName(filePath);

        try
        {
            Application ap = new Application();
            Document document = ap.Documents.Open(filePath);
            document.Fields.Update();

            foreach (Section section in document.Sections)
            {
                document.TrackRevisions = false;
                HeadersFooters headers = section.Headers;  //Get all headers
                foreach (HeaderFooter header in headers)
                {
                    Fields fields = header.Range.Fields;
                    foreach (Field field in fields)
                    {
                        // Här har du fälten i headern. Kolla om det är den du vill uppdatera. Tex
                      if (field.Type == Microsoft.Office.Interop.Word.WdFieldType.wdFieldUserName)
                      {
                          field.Select();
                          field.Delete();
                          document.Selection.TypeText("Johan Eriksson");
                      }
                      
                      // Osv med uppdateringar
                      
                      field.Update();
                    }
                }
            }    

            document.Save();
            document.Close();

        }
        catch (NullReferenceException)
        {
            System.Windows.Forms.MessageBox.Show("A valid file was not selected.");
        }
    }
}