Sharepoint Workflow task with title (external participant)

I made a custom sharepoint workflow with Visual studio, the workflow starts when a new item is inserted in a list

I assigned the title of the task to reference a field in the new item

TaskProps.Title = "Please prepare Hardware for project " + workflowProperties.Item["Contract"].ToString().Split('#')[1];

the task title is correct but i find the string (exteranl participant) concatenated the title of the task

what can be 开发者_开发技巧the reason for this ?

thanks

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SharePoint thinks that that Variable assigned(User) "Assigned To" is not a internal SharePoint user but external to the environment.