Question

Kind a simple problem, but i am completely lost on how to approach to this.

CREATE TABLE Contract (
  id int PRIMARY KEY,
  batchId int NOT NULL REFERENCES ContractBatch (id)
  campaignId int NULL REFERENCES Campaign (id)
)

This is simplified table in my business model, made to Linq2Sql model. Now i need to do update query like this:

UPDATE Contract SET campaignId = 1 WHERE batchId = 5

That means, there can be more records for same ContractBatch and i need to set Campaign for all of them. Is it possible to convert this query to Linq expression in some easy way ? Only way i am able find is fetch all those records for that ContractBatch and then update one by one in loop. That’s not very efficient.

var campaignId = 1;
var batchId = 5;
using( var dataContext = new DataModel.ModelDataContext() ) {
    dataContext.Contracts
        .Where( c => c.BatchId == batchId )
        // this is obviously my "wish to have" method
        .ForEach( c => c.CampaignId = campaignId )
    dataContext.SubmitChanges()
}

I am already thinking about doing it in old way and execute that query by hand. I don’t like it, but it’s probably better than running like hundreds of update queries.

Answer 1

You are right that there are two problems with this approach – you will be executing hundreds of individual update statements, and you have to read them in the first place to do the change.

This is a common weakness in ORMs.

Following a few google links I found the following blog post, which does have some interesting things to say in this area:
http://www.aneyfamily.com/terryandann/post/2008/04/Batch-Updates-and-Deletes-with-LINQ-to-SQL.aspx