Expression Builder

Use the Expression Builder dialog box to create and edit a property expression or write the expression that sets the value of a variable using a graphical user interface that lists variables and provides a built-in reference to the functions, type casts, and operators that the Integration Services expression language includes.

A property expression is an expression that is assigned to a property. When the expression is evaluated, the property is dynamically updated to use the evaluation result of the expression. Likewise, an expression that is used in a variable enables the variable value to be updated with the evaluation result of the expression.

There are many ways to use expressions:

• Tasks   Update the To line that a Send Mail task uses by inserting an e-mail address that is stored in a variable; or update the Subject line by concatenating a string such as "Sales for: " and the current date returned by the GETDATE function.
  
• Variables   Set the value of a variable to the current month by using an expression like DATEPART("mm",GETDATE()); or set the value of a string by concatenating the string literal and the current date by using the expression "Today's date is " + (DT_WSTR,30)(GETDATE()).
  
• Connection Managers   Set the code page of a Flat File connection manager by using a variable that contains a different code page identifier; or specify the number of rows in the data file to skip by entering a positive integer like 3 in the expression.
  

To learn more about property expressions and writing expressions, see Using Property Expressions in Packages and Integration Services Expression Reference.