automatic paging functionality in C#

Question

I am confused with a flow. I have a list of student objects.

List<Student> StudentLists;

Intially i will be having 10 student objects in the list.

There is a button in C# 4.0 winform and when i clicks on the button,

i need to take first 3 student objects from the list and call a wcf service and send these three student object to the wcf service.

I have implemented the wcf call back functionality.

After processing the web service, i will get the call back result for theose 3 student objects.

Each call back may come in different times.

Once i got all the three call back results from webservice, i want to take next 3 available student object and do the same web service call...

I want to do it untill it processes all the 10 items from the lists.

But I know how to take each time 3 objects from the lists. It is like paging.

var students = StudentLists.Skip(skip).Take(3).ToArray();

But I am doing it in each time button click. In each button click, i will take next 3 objects.

Is there any way that to do all these steps without doing button click ?

Answer 1

Seems like you want to process the students in batches, if this is the case you could write an extension method to do this:

public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> items, int batchSize)
{
    return items.Select((item, inx) => new { item, inx })
                .GroupBy(x => x.inx / batchSize)
                .Select(g => g.Select(x => x.item));
}

Usage:

foreach (var batch in StudentLists.Batch(3))
{
      //Do something with batch
      //Process
      //Get result etc...
}