The Expression Task is used to set variables and call functions using our extensive expression engine. Each action is evaluated in the order they appear in the grid.
The action this step in the expression task performs. There are five actions that can be performed:
Set Variable - This action sets the variable to the value entered in the Value/Expression column.
Set Variable From Expression - This action sets the variable to the result of the value returned from the expression in the Value/Expression column.
Set Variable and Replace Placeholders - This action sets the variable to the value entered in the Value/Expression column as well as replace any variable place holders in the text.
Replace Placeholders - This action replaces any placeholders that are part of the variable selected in the Variable column.
Call Function - This action executes the expression set in the Value/Expression column.
If the action requires you to select a variable, a drop down with all user defined variables displays.
Depending on the action, this contains either a static value or an expression that executes at runtime.
Selecting this button validates all the expression set in the Value/Expression column.
Selecting this button executes the selected expression using temporary values.
The Expression Editor is used to create and edit expressions that are used in any expression engine in a Task Factory task.
Columns / Variables Tab
The Columns/Variables tab list all of the columns available for the current component being edited, the variables and parameters and the connection managers available for the package. The columns node also lists any variable expressions defined for the current component. Any icon in the tree view that has a green icon next to it means it is being used by an expression.
The Functions tab lists all of the available functions that can be used in the advanced derived column. All functions are grouped into an appropriate group based on what the function either does or returns.
The Expression Editor is used to define the expression for the column or variable expression. The syntax highlighting makes it easy to recognize the functions you are using in the expression. You can use multi-line expressions and add comments to your expressions by using the /* */ syntax. Any column, connect, or function can be dragged and dropped from the tree view to the Expression window.
Validate / Test Expression Buttons
The expression editor allows you to validate and test your expressions during design time. The results appear in the Result tab.