Question

I have a method where I READ objects from DB, for instance:

public Object getProduct(int categoryId, int productId)
{
        DataClassesDataContext db = new DataClassesDataContext(Settings.getDefaultConnectionStringName());

        switch (categoryId)
        {
            case CCategorii.CARTI_ID:
                {
                    IEnumerable<Carti> product = (from c in db.Cartis
                                                  where c.Carti_id == productId
                                                  && c.Vizibil == true
                                                  select c);

                    if (product.Count() != 0)
                        return product.First();

                    break;
                }
           //so on
        }
}

Now I have another method where I do the update:

public void updateProduct()
{
   Object productToBeUpdated = getProduct(1,1);
    DataClassesDataContext db = new DataClassesDataContext(Settings.getDefaultConnectionStringName());
   //update some properties of the product
   productToBeUpdated.setQuantity(productToBeUpdated.getQuantity()+1);
   db.submitChanges();
}

Well, the product was succcesfully read from previous method but changes were not done into the DB.

I think the cause is that I do this READ-UPDATE in two different DataContext…If this is the cause how do you threat this situations?

Oh yeah, I can read the product and update in the same method but this means to duplicate the method I use for reading and add to it update stuff… and I would like to avoid this.

Answer 1

You are using two different instances of your DataContext.

When implementing a web app, the best option is usually to align the lifetime of your DataContext to the lifetime of one http request. The lifetime you use is just too short.

Another option is to attach the object to the write DataContext:

db.Cartis.Attach(yourReadObject);
updateProperties(yourReadObject);
db.submitChanges();

EDIT

Ok, you have to detach the object from your other context first. See this article on how to do it.

But i really would recommend to use a single DataContext object and extend the lifetime to the httprequest scope.

This can be done really nice with an ioc container like autofac.