Three important concepts we will use in this chapter are conditions, rules, and rule sets. In WF, conditions are chunks of logic that return true or false. A number of WF activities utilize conditions to guide their behavior. These activities include the While activity, the IfElseBranch activity, and the ConditionedActivityGroup. The While activity, for instance, loops until its Condition property returns false. We can implement conditions in code or in XML.
Rules are conditions with a set of actions to perform. Rules use a declarative if-then-else style, where the if is a condition to evaluate. If the condition evaluates to true, the runtime performs the then actions, otherwise the else actions. While this sounds like procedural code, there are substantial differences. The if-then-else constructs in most languages actively change the flow of control in an application. Rules, on the other hand, passively wait for an execution engine to evaluate their logic...