linq query to group the items

Question

var sales = _salesService.GetSales(parameters)

The list is something like

var listSales = new List<SalesData>();
listSales .Add(new SalesData
{
    Name = "Apple",
    Quantity = 1000
});
listSales .Add(new SalesData
{
    Name = "Banana",
    Quantity = 2000
});
listSales .Add(new SalesData
{
    Name = "Peach",
    Quantity = 1
});
listSales .Add(new SalesData
{
    Name = "Mango",
    Quantity = 1
});

I want to write a linq query so that I can group the 'Name' as 'Others' if the quantity is less than 1 percent of the total quantity.

So result of the query should be something like

Apple  56
Banana 23
Others 2  -- ( peach's quantity less than than 1% + Mango Quantity less than 1%)

Will there ever be two entries with the same name in the original data, e.g. two for Banana? — Jon Skeet, Dec 11 '14 at 08:43
Also, your example doesn't work - because you've got a total quantity of 81 items, so both Mango and Peach are above 1% of that quantity... — Jon Skeet, Dec 11 '14 at 08:44
please ignore the figures..applogies for that...The names will be unique in the list thanks. — freeCoder52511, Dec 11 '14 at 08:47

score 3 · Accepted Answer · answered Dec 11 '14 at 08:49

3

Well, it sounds like first you need to know the total quantity. That's easy enough:

var total = listSales.Sum(entry => entry.Quantity);

Then you need to work out the cutoff point, which is 1% of it:

var cutoff = total / 100;

For the grouping and summing, I'd probably go in three steps:

Transform the original list into a sequence with entries of "Others"
Group entries by name
Sum per group

So the overall code would be:

var total = listSales.Sum(entry => entry.Quantity);
// TODO: Work out whether you want the cutoff to be exclusive or not.
var cutoff = total / 100;
var results = listSales.Select(entry => entry.Quantity >= cutoff ?
                                            entry :
                                            new SalesData { 
                                                Name = "Others",
                                                Quantity = entry.Quantity
                                            })
                       .GroupBy(entry => entry.Name, entry => entry.Quantity)
                       .Select(group => new { Name = group.Key,
                                              Total = group.Sum() });

You can combine the "group and select" operations, but personally I find the above simpler to read.

answered Dec 11 '14 at 08:49

Jon Skeet

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thanks..any tips for improving my linq?? I am new to it. – freeCoder52511 Dec 11 '14 at 08:57
@freeCoder52511: It's mostly practice, in my experience. It definitely gets easier over time. It's also worth becoming familiar with both "lambda syntax" (as here) and query expressions. – Jon Skeet Dec 11 '14 at 09:09
Hi jon..what if I Want to select one more additional row. for eg select name, total and Trade. thanks – freeCoder52511 Dec 17 '14 at 17:17
@freeCoder52511: Well where would the trade come from? You're grouping by name, so there could be multiple values with different trades within the same group. If you want to group by name *and* trade, use an anonymous type - `GroupBy(entry => new { entry.Name, entry.Trade }` – Jon Skeet Dec 17 '14 at 17:27
great! sorry thats what I meant..wanted to group by name and trade. – freeCoder52511 Dec 17 '14 at 17:56

linq query to group the items

1 Answers1