Note that this example assumes that you have a MongoDB connection string, a MongoClient object named client, a database name, a collection name, and a RichTextBox control named myRichTextBox.

Also note that if you want to store formatted rich text (such as bold or italic text), you will need to use a markup language such as HTML or Markdown to encode the formatting. When you retrieve the rich text from MongoDB, you can then use a library or tool to convert the markup back into formatted text.