Question

I’m in the process of rewriting our application. We are building DataMappers to work in our DAL. My question relates to the situation where I have a complex object from the BLL that get’s passed to the DataMapper to be persisted.

Let’s say this object has a lot’s of properties including lists of other objects.

i.e…

public class Customer
{
    public String name;
    public String age;
    public String ShoeSize;
    public List<Address> a;
    public List<Orders> o;
{

In a situation where maybe “age” was the only field that was updated in the BLL.

What’s a good practice for persisting this to the database?

Would you persist the entire structure? or How can I structure this so that my DataMapper would know which fields changed so that I didn’t have to update the entire structure in the database? I guess I could have some kind of IsDirty field for each property, but that could get messy really quick.

Thanks,

MW

Answer 1

If you keep the original object in memory and pass in a new “version” with the changes, you could check the new object for changes and only save that.

public class CustomerMapper {
    // ...
    public void Update(Customer original, Customer update)
    {
        // check each property for changes
    }
    // ...
}

After the update you replace the original object with the new. But be aware of concurrency issues if you have multiple threads.