The identity of the SPContentType property that is associated with the task list item.
Assembly: Microsoft.SharePoint.WorkflowActions (in Microsoft.SharePoint.WorkflowActions.dll)
Content type identifiers (IDs) are unique IDs that are expressed in hexadecimal format. They are structured in a way that allows the ID to contain unique information about itself, and also its hierarchical relationships. When you view the child content type, you can determine from which parent content type it is derived.
The ContentTypeId that is specified for this activity can be either one of the built-in content types or any of the custom types.