When retrieving a machine property in the Workflow Designer of vCAC that does not exist and later on access the internal workflow variable holding that machine property value you will receive a “System.NullReferenceException”.

[UTC:21/07/13 13:11:30.255 Local:21/07 15:11] [Error]: <?xml version="1.0" encoding="utf-16"?>
Workflow "WFStubMachineProvisioned" failed with the following exception:
System.NullReferenceException: Object reference not set to an instance of an object.
   at lambda_method(Closure , ActivityContext )
   at Microsoft.VisualBasic.Activities.VisualBasicValue`1.Execute(CodeActivityContext context)
   at System.Activities.CodeActivity`1.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager)
   at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)

When using a “TryCatch” activity to react upon this condition an exception is only triggered when you set “Is Required” to “True” (regardless of what you defined in your catch block).

VCAC TryCatch Activity
VCAC TryCatch Activity with GetMachineProperty and “Is Required” = True

As a workaround for you can also pre-initialise the variables in your workflow and then you might not have to use the “TryCatch” activity at all.

VCAC PreInitialise Variables
VCAC PreInitialise Variables

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