WCF Data Services and Upserts

Question

I have a WCF Data Services with an entity named Contract.

there is a many to many between Contracts and Quotes : ( * ) Contract <----> ( * ) Quotes

I have a method that adds/remove links between contracts and quotes.

and sometimes I get an updateException because I'm trying to add a link between a Contract and a Quote when the link is already existent.

I want to write a query that adds a link only if the link doesn't exist yet without needing to query the database for the existing links between my contract and quotes.

Is there a way of doing that using Expression Trees ? or Linq ?

At the moment, I do this :

void ModifyContract(Contract ctr)
{
    var contractInDb = (from c in service.Contracts.Expand("Quotes")
                       where c.Id == ctr.Id).Single();

    foreach(q in ctr.Quotes)
    {
        if( ! contractInDb.Quotes.Contains(q))
         {
              service.AddLink(ctr,"Quotes", q);
         }
    }

    service.SaveChanges();
}

When you say that the link already exists, to you mean that it already exists in the database, or in memory? If you mean the database, there is no way on the client side to know which links are in the database without querying the database... — therealmitchconnors

Gone Coding Gone Coding · Accepted Answer · 2011-06-24T14:29:50

I asked a similar question myself for Silverlight How to do a server-side Insert/Update (Upsert) from Silverlight RIA services

You either need to check for an existing relationship (then it is just down to how efficient you can make it), or you can put your Upsert functionality into a stored procedure (e.g. sp_UpsertQuote(contractId, quoteId) and call that instead of using SaveChanges().

WCF Data Services and Upserts

2 Answers