Question

I’m using EF 4.1 (Code First). I need to add/update products in a database based on data from an Excel file. Discussing here, one way to achieve this is to use dbContext.Products.ToList() to force loading all products from the database then use db.Products.Local.FirstOrDefault(…) to check if product from Excel exists in database and proceed accordingly with an insert or add. This is only one round-trip.

Now, my problem is there are two many products in the database so it’s not possible to load all products in memory. What’s the way to achieve this without multiplying round-trips to the database. My understanding is that if I just do a search with db.Products.FirstOrDefault(…) for each excel product to process, this will perform a round-trip each time even if I issue the statement for the exact same product several times ! What’s the purpose of the EF caching objects and returning the cached value if it goes to the database anyway !

Answer 1

There is actually no way to make this better. EF is not a good solution for this kind of tasks. You must know if product already exists in database to use correct operation so you always need to do additional query – you can group multiple products to single query using .Contains (like SQL IN) but that will solve only check problem. The worse problem is that each INSERT or UPDATE is executed in separate roundtrip as well and there is no way to solve this because EF doesn’t support command batching.

Create stored procedure and pass information about product to that stored procedure. The stored procedure will perform insert or update based on the existence of the record in the database.

You can even use some more advanced features like table valued parameters to pass multiple records from excel into procedure with single call or import Excel to temporary table (for example with SSIS) and process them all directly on SQL server. As last you can use bulk insert to get all records to special import table and again process them with single stored procedures call.