Comparing large list of objects

Question

I have a form that contains a list of objects that are all updated at once. In the controller, a nested loop compares each model to the other models so it can determine which objects have been updated and which are new.

foreach(var x in formObject)
{
    foreach(var y in dbObject)
    {
        if(x.id == y.id)
        {
             //compare each property and notify user of change if different
        }
    }
}

This takes a huge amount of time considering the large number of objects and how slow the servers are.

Is there a better practice for doing this? Some way of determining which objects have been updated before looping through all? Or a more efficient loop?

Answer 1

You could use a join in Linq:

var differences = 
    from x in formObject
    join y in dbObject on x.id equals y.id
    where ( /* compare each property */ )
    select new { /* what do you want to tell the user */ };

Of course, without more information about what's in the loop, that's just about all the code I could provide.

In fluent syntax that would be:

var differences =
    formObject.Join(dbObject, x => x.id, y => y.id, (x, y) => new { x, y })
              .Where(p => /* compare properties of p.x and p.y */)
              .Select(p => new { /* what do you want to tell the user */ });