Question

I have a list that looks something like this:

catId    itemId    value
  1        5         "some text"
  1        19        "some text"
  1        21        "some text"
  2        6         "some text"
  2        8         "some text"
  3        9         "some text"
  3        82        "some text"

Notice the catId column. How would I take 2 rows(or remove extra rows) for each unique value in the first colum. Only 2 rows for catId=1 2 rows for catId=2 and so on?

My list is called distinctXSelling and I’m using it like this currently:

            foreach (var item in distinctXSelling)
            {
                xSelling.InnerHtml += item.value;
            }

Answer 1

You can group items by their category-id and then pick the first two items from each group, before flattening the sequence of groups into a sequence of source-items. This would look like:

var query = source.GroupBy(item => item.catId)
                  .SelectMany(catGroup => catGroup.Take(2));

Note that the Take method takes upto a certain number of items, so this won’t throw if a category has only a single item.

As BrokenGlass points out, you might need a .OrderBy (and possibly a .ThenBy) if you want the filtered items out in a specific order.

You might also want to consider replacing the loop with:

xSelling.InnerHtml = string.Concat(query.Select(item => item.value));