Text Size
Originally Published inI am back again from the Autodesk European Football Tournament 2011 ↗ in Verona, Italy, vividly described in more detail by Kean on his blog. We were both part of the combined Global Services (to which we of ADN belong) and Worldwide Marketing team:

Back to the Revit API, we already looked at some aspects of text formatting such as textnote alignment and rotation. Here is a still more immediate and simpler issue:
Question: I created some text using the NewTextNote method. Now I would like to change its size or font like a normal user might do using Edit type > Text size. How can that be achieved programmatically?
Answer: The Text Size parameter can be set as follows:
Reference r = uidoc.Selection.PickObject(
ObjectType.Element );
TextElement text = doc.GetElement( r )
as TextElement;
TextElementType textType = text.Symbol;
Parameter textSize = textType.get_Parameter(
"Text Size" );
Transaction transaction
= new Transaction( doc );
transaction.Start( "change text size" );
// units are in feet, so this is 1/8"
double newSize = ( 1.0 / 8.0 ) * ( 1.0 / 12.0 );
textSize.Set( newSize );
transaction.Commit();
Obviously, it would be better still to use the built-in parameter enumeration value to identify the text size parameter, rather than the language dependent user display parameter name.