HomeController.cs

[HttpPost]
public string LoadTemplate(LoadDocumentViewModel model)
{
    byte[] data;

    using (TXTextControl.ServerTextControl tx =
      new TXTextControl.ServerTextControl())
    {
        tx.Create();

        TXTextControl.StreamType streamType =
          TXTextControl.StreamType.WordprocessingML;

        switch(Path.GetExtension(model.DocumentName))
        {
            case ".doc":
                streamType = TXTextControl.StreamType.MSWord;
                break;
            case ".rtf":
                streamType = TXTextControl.StreamType.RichTextFormat;
                break;
            case ".tx":
                streamType = TXTextControl.StreamType.InternalUnicodeFormat;
                break;
            case ".pdf":
                streamType = TXTextControl.StreamType.AdobePDF;
                break;
        }

        tx.Load(Server.MapPath("/App_Data/documents/" +
          model.DocumentName), streamType);

        tx.Save(out data,
          TXTextControl.BinaryStreamType.InternalUnicodeFormat);
    }

    return Convert.ToBase64String(data);
}