Creating Expressions for Properties of Data Flow Objects
To specify a property expression for one of the properties of data flow objects listed in this topic, display the Properties window for the Data Flow task by selecting the Data Flow task on the Control Flow surface of the designer, or by selecting the Data Flow tab of the designer without selecting any individual component or path. Select the Expressions property and click the ellipsis (...) to display the Property Expressions Editor dialog box. Drop down the Property list to select a property, then type an expression in the Expression text box, or click the ellipsis (...) to display the Expression Builder dialog box.
The Property list displays available properties for only those data flow objects that you have already placed on the Data Flow surface of the designer. Therefore, you cannot use the Property list to view all the possible properties of data flow objects that support property expressions. For example, if you have placed an ADO NET source on the designer surface, the Property list contains an entry for the [ADO NET Source].[SqlCommand] property. The list also displays many properties of the Data Flow task itself.