The text wraps to a new line. If you have enough space to show more than one line, there will always be some text visible (see Demo/Composite Nodes).

You should be able to scroll up or down using arrow keys, but make sure the key events actually reach the DiagramView. E.g. check if you aren't consuming arrow key events from PreviewKeyDown event handler. If DiagramView is inside a user control, the parent control might be doing that internally (https://stackoverflow.com/questions/6177201/how-to-prevent-usercontrol-form-hand...).

You might try setting EditComponent's ScrollFirstLine property to 0 after editing text to make sure it shows the first line.

Regards,
Slavcho
Mindfusion

I was able to do it by overriding the OnKeyDown method. It would be nice if there was a Cancel or Handled property.