Design time validation is turned off. Validation occurs only at runtime. To validate your workflow, either enable validation ...

Design time validation is turned off. Validation occurs only at runtime. To validate your workflow, either enable validation by modifying the registry key[HKCU\Software\Microsoft\.NETFramework\v[assembly version]\System.Activities.Presentation\DisableValidateOnModelItemChanged] and reopening the designer or call ActivityValidationServices.Validate() on an instance of your workflow.