@Html.TXTextControl().DocumentViewer(settings =>
{
    settings.DocumentPath = Server.MapPath("~/App_Data/Documents/gallery_merging-images.tx");
    settings.Dock = DocumentViewerSettings.DockStyle.Fill;
    settings.IsSelectionActivated = false;
    settings.ShowThumbnailPane = false;
}).Render()

<button onclick="Merge('gallery_merging-images.tx')" class="btn mt-3 btn-success">Merge Template</button>