The C1RichTextBox is considered like a TextBox, like you can get and set the text and write to files yourself.
I’ve attached a sample that shows how to read and write to HTML/RTF files using C1RichTextBox.
Here is the key code to save a file:
private async void btnSave_Click(object sender, RoutedEventArgs e) { FileSavePicker savePicker = new FileSavePicker(); savePicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary; savePicker.FileTypeChoices.Add("HTML Page (*.html)", new List<string>() { ".html", ".htm" }); savePicker.FileTypeChoices.Add("Rich Text Format (*.rtf)", new List<string>() { ".rtf" }); savePicker.DefaultFileExtension = ".html"; StorageFile file = await savePicker.PickSaveFileAsync(); if (file != null) { if (file.FileType.Equals(".html") || file.FileType.Equals(".htm")) { // Save HTML await FileIO.WriteTextAsync(file, c1RichTextBox1.GetHtml(HtmlEncoding.StyleSheet)); } else if (file.FileType.Equals(".rtf")) { // Save RTF await FileIO.WriteTextAsync(file, new RtfFilter().ConvertFromDocument(c1RichTextBox1.Document)); } } }