The file '{0}' may have come from a location that isn't fully trusted. It could present a security risk by opening the file ...

The file '{0}' may have come from a location that isn't fully trusted. It could present a security risk by opening the file that could cause damage to your computer or compromise your private information.
To avoid this exception, please do the security check first (you can refer this link http://msdn.microsoft.com/library/system.security.permissionset.aspx to get information about IsUnrestricted check) and turn on LoadingFromUntrustedSourceEnabled by setting DesignerConfigurationService.LoadingFromUntrustedSourceEnabled = true from workflow designer.