We currently use version 184.108.40.206786 of the GroupDocs Viewer for .NET to show a preview of documents. Unfortunately we experience problems in some text files coded in UTF-8: The German umlauts are not rendered correctly (see attached screenshot). I have added the corresponding text file so you can hopefully reproduce this behavior. Is there a way to set the file encoding for the viewer component? Currently we just set the path to the file to display, i.e. ViewerUserControl.ContentDisplay.OpenDocument(path).
This issues seems similar to VIEWERJAVA-739.