SPWorkflowAssociation.AssociationData Property
Gets or sets the association data for workflow instances based on this workflow association.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Available in Sandboxed Solutions: Yes
Available in SharePoint Online
Association data is any custom data to pass to the workflow association form. It is recommended but not required that the data be valid XML. The association form that you specify for the workflow must be able to parse the data.
For more information, see Workflow Association and Initiation Forms (Sharepoint Foundation).