Se ha generado un id. de instancia para WorkflowApplication porque la propiedad 'Id' era de lectura. No se puede usar WorkflowApplication para cargar una instancia una vez que se ha generado un id.
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English version
An instance ID has been generated for the WorkflowApplication because the 'Id' property was read. WorkflowApplication cannot be used to load an instance once an ID has been generated.
.Net Framework