Understanding Expressions

Overview

Sequence expressions are sophisticated and flexible tools for retrieving the information you need in workflows. An expression is a .NET compiled method, and is always typed. You can use Sequence expressions for the following actions.

  • Create complex business rules
  • Easily define default values for fields on forms
  • Generate dynamic workflow messages
  • User workflow and activity data and metadata while integrating with other systems
  • Integrate with SQL queries
  • Obtain runtime data  (including HTTP request, and a user's information)


Expression Building Blocks


Sequence expressions are composed of building blocks, which are typed objects, whose properties, methods, and functions are accessible.

Expression Markup Types

There are several ways to write expressions in a form's markup, each with a different function.

Expression Markup TypeDescription
Expression Markup Types
<%$ sq:{...}%>
The expression is calculated during the build of the control tree, so it might execute twice, but will always work.
<%#{...}%>
The expression is executed only as part of the control's binding. Some controls have different binding order, so execution might fail.
<%= {...}%>
The expression is calculated on each page render, but cannot be sued as a control property.