I am creating a Solidworks Add-in that integrates with Solidworks PDM Professional using C# and I am getting an error in my code i cant figure out how to solve.

in this bit of code i get an error of at batch.UpdateReferences(addRefs, removeRefs);

how can i fix this

                    IEdmBatchItemReferenceUpdate batch = default(IEdmBatchItemReferenceUpdate);

                    batch = (IEdmBatchItemReferenceUpdate)vault1.CreateUtility(EdmUtility.EdmUtil_BatchItemReferenceUpdate);

                    batch.UpdateReferences(addRefs, removeRefs);