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What this segment does is check whether the user exists in the AD or not, and if it doesn't, it will create the user in a TryCatch activity. If the user exists, the workflow will stop executing and display an error message (in our case: "Error: user already exists.").
Tracking data:
Rethrow
This activity contains activities to be executed by the workflow runtime in an exception handling block.
The purpose of this activity is to enclose another activity or group of activities that are prone to throwing exceptions and therefore stop the workflow with unknown results. One can
Activity Parameters
The TryCatch activity has has no parameters other than its DisplayName that can be changed for easier comprehension of the workflow/area it's in.
Example: