SPRelatedField.ListId property

Gets the identifier of the child list that is dependent on the parent list.

Namespace:  Microsoft.SharePoint
Assembly:  Microsoft.SharePoint (in Microsoft.SharePoint.dll)

public Guid ListId { get; }

Property value

Type: System.Guid
The value of the ID property of the dependent list.

The list that is identified by the ListId property has lookup fields that point to fields in the list represented by the LookupList property.