Yes you can define conditions in workflow by using conditionedActivitygroup. Below is the numbered snapshot which shows how to use conditionedActivitygroup.
1 - You can see in this snapshot we have defined a conditionedActivitygroup with two conditions. The two boxes inside the group define two conditions.
2 - You can select one of the condition box and define the condition using the WhenConditions property. If this condition is true you need to specify in the execute code which method to execute. For instance in the current snapshot we have said that old1 method should execute if age > 21. The same procedure we need to follow for the second condition box. In the second condition box we have specified to execute young1 method if age <>3 - Workflow editor also provides a cool interface called as Rule Condition Editor which can be used to specify conditions. Age is a public property in the behind code. You can also get the Age in the intellisense of rule condition editor.
4 - Both the condition will execute inside the condition activity group. We need to also specify when this conditionactivitygroup should exit. So we have made a function called as exit. If the user inputs age as -1 it will exit from the loop or else it will take inputs from user and continue evaluating depending on the two conditions.