Changing the height of a RadTextBox using the Multiline property

 
HOW-TO
Modify the height of a RadTextBox

SOLUTION
The height of the text box depends on the mode in which the text box is. RadTextBox can be switched between multiline and single-line modes via the Multiline property:

1. Single-line text box (default)
   The height is determined by the Font of the text box. To have additional space between the text area and the border, Padding can be used (its top and bottom parts). When the Padding is non-empty, the space outside of the text area is filled by a FillPrimitive. The properties of this FillPrimitive can be modified via a theme or directly in design time (via the "Element hierarchy editor"). By default, the GradientStyle is set to Solid (i.e. not a gradient) with a white ForeColor.
   It is important to keep in mind that when the height of the text is changed (due to a modification of the Font) - the height of the RadTextBox changes in order to accommodate the text.
    
2. Multiline
   The height can be freely modified both in design time and via code.