ActivityMetadata.AddVariable Method (Variable)
Adds the specified variable to the metadata’s collection of variables.
Assembly: System.Activities (in System.Activities.dll)
Variables added using this method are considered part of the activity’s publicly configurable surface, that is, they are to be provided by the consumer of the activity. For example, Sequence adds the variables in its Variables collection using this method. An activity’s implementation cannot access variables added using this method. Activities added through AddImportedChild (and any of their non-implementation child activities) can access variables added using this method. For example, Sequence adds its Activities collection in this manner.