( OData - Open Data Protocol - WCF Data Services - .NET 4.0 ) - Filtering with NULL -

I have the following problem, I need to find zero values ​​using data services.

In C # I use:

  Data service service & lt; Sync.Doctor & gt; DataServiceQuery as query = syncEnt.Docctors & lt; Sync.Doctor & gt ;; Query.AddQueryOption ("$ filter", "(ID and" + CurrentDoctor.Id + "and ((synch_date eq blank and deleted eq 0) or (updated_at gt synch_date))");  

Then it generates:

  http: //localhost/odata.svc/Doctors ()? $ Filter = (IDE 575504 and ((synch_date Eq null and deleted eq 0) or (updated_at gt synch_date)))  

But just this question has been put into the web browser, The following error occurs:

Operator 'eq'

Regards, Daniel Skoronsky

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