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I have a question about Saving a list of object in ASP.NET MVC. First I'm not using EntityFramework or Nh like ORM tool, just use Ado.net

suppose I have an object Product, and I want to collect all the products data via javascript and batch update the product list in one call.

my question is when should I differentiate which item is inserted, updated, or deleted?

  1. one strategy is that I have a enum property on the DTO object and also on the javascript ViewModel, and when I add an item into the viewModel, I marked this object to add, and if I changed one Item, I marked it to updated. so when this request come to the action, I can know which items to be insert or update.

    • pros: it's easy on server side, don't need to differentiate the object status from server side.
    • cons: if I want to publish this action to webapi that will be called by third party, that may need third party user to differentiate the state of the object.

  2. differentiate the data from server side, just give me a list of object, on the server side, first retrive the current data from database, compare the data, then check which record to be inserted or updated.

    • pros: all the compare are done from server side.
    • cons: proformance issue

  3. what ever the data passed from client, just remove the current data and insert the new data

I hope someone could give me an advice, what's the best practice to handle this situation, I think it's quite common but I can't find a best solution.

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    How much data are we talking about here? Commented Feb 28, 2013 at 4:23
  • it dependents, like Order with Order LineItems, maybe 10-20 line items in an order Commented Feb 28, 2013 at 4:26
  • Seems that if you have lots of data, send it across and do everything server side. If relatively small, mark your objects on the client where it's easier to do (closer to the source of the change). MY 2cp. Commented Feb 28, 2013 at 4:29

2 Answers 2

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I've seen option 1 where added/deleted/modified items are maintained in javascript arrays and posted back to server. But for some reason, I didn't like it maybe because of writing client side code to maintain state.

So, I had used second option and thanks to LINQ for making my task easier. Assuming list has some unique id, below is pseudo code. Note: newly added items should have unique random id's, otherwise there might be chance of treating them as already existing item. In my case its GUID, so there was no chance of overriding.

var submittedIds = vmList.Select(a=>a.Id).ToList();
var dbIds = dbList.Select(d=>d.Id).ToList();
//Added items
var newIds = submittedIds.Except(dbIds).ToList();
//loop over newIds and construct list object to contain newly added items 

//Deleted items
var deletedIds = dbIds.Except(submittedIds).ToList();
//Modified items
var modifiedIds = dbIds.Intersect(submittedIds).ToList();//if the values don't change, update statement won't do any harm here

This approach gives reasonable performance unless you are dealing with huge lists.

I think third option is not good. For ex: if you plan to implement audit features on your tables, it will give you wrong functionality. If a new record is inserted, you will have entries for all records as deleted and then one inserted which is wrong because only one is inserted.

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1

3rd strategy is suitable for simple situations e.g. when you want to update a Purchase Order items, an Order will not have too much OrderLineItems. However, you have to take care concurrency issue.

I think your first strategy is best suitable in general case. It's also easy to implement. When you want to publish your service to a 3rd party, it's usual that a client must follow the service definition and requirement.

Update

For 1st strategy: If you don't want your clients have to specify status for their data, then do it for them. You can separate the SaveOrder service into smaller services: CreateOrder, UpdateOrder, DeleteOrder.

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ya, I agree but the main problem I faced is like I said if I want to make it as a public API that need to be used by third party, OrderService.SaveOrder(Order); then I may need to tell third party, please differentiate your data first, and indicate the state of the lineItems (update or insert), it's not quite friendly.....
ya, the Order Object is a graphy object has a nevigate list of OrderLineItems, even separate into smaller services, when updateorder ,we still need to know the status of order LineItem, unless we separate the service to UpdateOrderLineItem createorderlineItem ect... do you mean that?

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