how to adding to annotation entity from OrganizationServiceClient in dynamics crm 2011?

Hi All,

I trying to add annotation from my web service, I use crm service discovery /  OrganizationServiceClient, I used the HelperCode from SDK but I got an error, and can not to compile.

on below is my codes:

Annotation anno = new Annotation();
anno.ObjectId = new Microsoft.Xrm.Sdk.EntityReference() { Id = _headerId, LogicalName = name};
anno.ObjectTypeCode = name;
anno.Subject = "Notes From NAV";
anno.NoteText = reason;
client.Create(anno);

please advise.

thanks

glo.