[Simple introduction to WF] -- Use of activity parameters and variables

Code:
Overview
Data is transmitted through the use of variables.
Variables and parameters used in the activity
[In parameter]. The value of the correlated variable can be passed In. When the parameter is modified internally, the correlated variable is not changed.
[Out parameter] The correlated variable value cannot be passed in. When an internal parameter is modified, the associated variable is updated.
The value of the [In/Out parameter] correlated variable can be passed In. When the internal parameter is modified, the associated variable is updated.
The preceding parameters can be modified using the [RequiredArgument] feature.
Variable outside the activity
Scenario: Activity A is nested with activity B. Variables In activity A can interact with each other through the [In parameter] of Activity B and output through the [Out parameter] of Activity B.
This Variable in activity A can be regarded as A global Variable. It must inherit the class System. Activities. Variable <T>.
References:
Instance: WF_WCF_Samples \ WF \ Basic \ CustomActivities \ Code-Bodied \ HelloWorld