A while ago I wrote some advanced TextBox windows controls:
- MutliTextbox - Designed to split a single big window into multiple sections, just like splitting an Excel worksheet into multiple views.
- FileTextBox - Designed to easily load and save files to the text area.
These take advantage of WinForms ability to write your own custom controls. These are standard Windows User Controls (System.Windows.Forms.UserControl). Such controls can be added to the toolbox under the "UserControls" tab, and have full design support.
Both of these are free controls at: http://www.timstall.com/Code/WinControls.aspx. I find these useful when I making my own tools.