About expressions in derived or unbound properties

An expression can be used in a derived or unbound IDO property to convey the value of the property when the property is used.

Expressions used in IDO properties must be SQL expressions that are used to define the value of the property, and that can be evaluated as SQL SELECT statements. The expression is evaluated when data is selected from the table.

The expression can be used to perform calculations, sub-queries, or calls to SQL functions.

When used as part of an expression, property names are case-sensitive.

Expressions can be inherited from property classes. For example, suppose you have a property that uses this expression: Price * Quantity

You can create a property class that contains this expression, and then inherit it in an IDO property that uses that property class. This effectively makes it reusable; that is, you can create multiple properties that inherit from this property class and inherit this expression.

To make them even more flexible and reusable, not only can expressions be inherited, but they can also be "parameterized". So, you could change the expression to something like this: {0} * {1}

To do this, use the {n} format to specify placeholders for the parameter values.

This means that, from a derived property, for instance, you can specify the arguments “Price, Quantity”, and these arguments are substituted into the parameters when the property is used.

Note: Parameters are zero-based indexes, and the arguments are presented as a comma-delimited list. So, in this example, "Price" corresponds to parameter {0} and "Quantity" corresponds to parameter {1}.