A named expression is a composed of the following:

• expression — the text string that is to be evaluated. The expression is a single-line statement that contains symbols and operators and optionally, numbers (integer or double-precision real) and strings. The statement syntax is shown below.
• internal name — name stored in the DGN library. The internal name should not be changed once the expression is used to define a conditional test.
• external name — defines the string that is displayed in the drop-down menus used to select a named expression for evaluation. This name can be localized to other languages.
• description — visible only in the Named Expressions dialog.
• keyword list — used to group and filter named expressions.
• symbol set list — used to evaluate a named expression.

Examples of expressions:

(symbol or value) [operator (symbol or value) [operator
(symbol or value)…..]]
1
1+1
1+1+1
"Hello World!"
"Active Model:" & ActiveModel.Name
"Active Model:" & ActiveModel.Name & " Time:" &
System.DateTime.Now()

For more examples, see Operators in named expressions.