Develop Reference

How to get dictinct userid with order by close using Linq

I have table called info, and its data something like this:
FKUserID
CompletedTime
Type
1
2021-03-10 12:56:00.423
5
245
2021-03-10 12:46:46.977
5
1
2021-03-10 12:44:53.683
5
1
2021-03-10 12:40:54.733
5
1
2021-03-10 12:35:26.307
5
245
2021-03-10 11:11:33.887
5
245
2021-03-10 10:18:11.403
5
I need to get distinct userID data, and also with the maximum completed time of theirs CompletedTime column
expected output is:
FKUserID
CompletedTime
Type
1
2021-03-10 12:56:00.423
5
245
2021-03-10 12:46:46.977
5
I need to do this using Linq query
How can I do this, I did it using SQl, need it using Linq
SELECT FKUserID , MAX(CompletedTime)
from Info
where cast(CompletedTime as date) = '2021-03-10'
and Status = 5
GROUP BY FKUserID;

You can use the following query. The following query implements your SQL query.
var query = context.Info.GroupBy(a => a.FKUserID)
.Join(context.Info,
left => left.Key,
right => right.FKUserID,
(left, right) => new { left, right })
.Where(a => a.right.CompletedTime.ToShortDateString() == "2021-03-10" && a.right.Status == 5)
.Select(a => new
{
FKUserID = a.left.Key,
CompletedTime = a.left.Max(x => x.CompletedTime)
}).ToList();

Something like this
var d = new DateTime(2021, 3, 10);
var d2 = d.AddDays(1);
dbContext.Infos
.Where(i => i.Status == 5 && i.CompletedTime >= d && i.CompletedTime < d2)
.GroupBy(i => i.FkUserId)
.Select(g => new {
FkUserId = g.Key,
CompletedTime = g.Max(g2 => g2.CompletedTime)
}
);

To Sum Value using linq

In the below code i have a list i am trying to get values from list using linq query and sum the values.But i don't know how to sum the values.So please help me to resolve the issue.
list contains:
Desc Month level value
M1 Jan L1 2
M1 Jan L2 6
M2 Feb L1 4
M2 Feb L2 1
My Expected Result:
M1 Jan 8
M2 Feb 5
var sums1 = objList
.GroupBy(y => new { y.Desc, y.Month, y.value })
.Select(group => new { KeyValue = group.Key, Count = group.Count() });

You shouldn't be including the value in your grouping - you want to group by just Desc and Month (I assume), then sum the value parts. Two options:
var sums1 = objList
.GroupBy(y => new { y.Desc, y.Month })
.Select(group => new { KeyValue = group.Key, Sum = group.Sum(y => y.value) });
Or in a single call:
var sums1 = objList.GroupBy(
y => new { y.Desc, y.Month },
(key, values) => new { key.Desc, key.Month, Sum = values.Sum(y => y.value) });

Replace your group.Count with group.Sum(x=>x.value)

Use LINQ's Sum() extension method for IEnumerable.
.Select(group => new { KeyValue = group.Key, Sum = group.Sum(obj => obj.value)});

LINQ multiple group by and then getting the first group by value count

I have a linq query like followin:
var _transactionsList = TransactionsData
.GroupBy(x => new { x.ItemID, x.Title, x.GalleryURL })
.Select(pr => new TransactionsTabResults
{
ItemID = pr.Key.ItemID,
Title = pr.Key.Title,
GalleryURL = pr.Key.GalleryURL,
ItemPrice = pr.OrderByDescending(a => a.TransactionDate).First().ItemPrice,
TotalSoldItems = pr.Count(),
TotalRevenuePerItem = pr.Sum(y => y.ItemPrice),
AveragePrice = pr.Average(y => y.ItemPrice),
}).ToList();
I'm trying to fetch the total sold items value by grouping it by like this:
ItemID Sales ItemName
1 1 Item1
1 3 Item1
1 5 Item1
1 6 Item1
2 2 Item2
2 2 Item2
2 2 Item2
2 2 Item2
The desired output would be:
ItemID Sales ItemName
1 15 Item1
2 8 Item2
The query above that I wrote gives me wrong values for total sales by saying:
TotalSoldItems = pr.Count(),
How can I count, or sum all the sales of one Item which has unique ID(this is what I'm grouping by)...
What am I doing wrong??

You are using GroubBy wrong way. You create new unique object every time. So your .GroupBy(x => new { x.ItemID, x.Title, x.GalleryURL }) and .Select(x => new { Key = new { x.ItemID, x.Title, x.GalleryURL}, Value =x }) means the same
If you need unique Id then group by Id only
TransactionsData
.GroupBy(x => x.ItemID)
.Select(pr => new TransactionsTabResults
{
ItemID = pr.Key,
Title = pr.First().Title,
GalleryURL = pr.First().GalleryURL,
ItemPrice = pr.OrderByDescending(a => a.TransactionDate).First().ItemPrice,
TotalSoldItems = pr.Count(),
TotalRevenuePerItem = pr.Sum(y => y.ItemPrice),
AveragePrice = pr.Average(y => y.ItemPrice),
}).ToList();
Advice
Optimize your LINQ. You are iterating through collections many times. This is suggested code:
TransactionsData
.GroupBy(x => x.ItemID)
.Select(pr =>
{
var items = x.pr.ToArray;
var sum = items.Sum(y => y.ItemPrice);
return new TransactionsTabResults
{
ItemID = pr.Key,
Title = items[0].Title,
GalleryURL = items[0].GalleryURL,
ItemPrice = pr.Aggregate((max, cur)=>max.TransactionDate<cur.TransactionDate?cur:max).ItemPrice,
TotalSoldItems = items.Length,
TotalRevenuePerItem = sum,
AveragePrice = sum/items.Length,
};
}).ToList();

c# Linq count group by

My getTrustActivitiesFromStorage List looks something this
venueId venueName activityId
1 Location1 Zumba
2 Location2 Yoga
1 Location1 Yoga
1 Location1 MetaFit
3 Location3 Zumba
Here's the code i use to group etc
List<TrustActivities> filteredVenues = new List<TrustActivities>();
IEnumerable<TrustActivities> groupedVenueCollection = getTrustActivitiesFromStorage
.GroupBy(customer => customer.venueName)
.Select(group => group.First())
.OrderBy(x => x.venueName);
// Loop
foreach (TrustActivities activity in groupedVenueCollection)
{
filteredVenues.Add(new TrustActivities
{
filterId = Convert.ToInt32(activity.venueId),
filterName = activity.venueName,
filterCount = 55
});
}
This successfully groups the list and outputs the 3 matches:
1 Location1 (55)
2 Location2 (55)
3 Location3 (55)
The final bit i need help with is counting each group, so filterCount = 55 will be replace with the dynamic count to give:
1 Location1 (3)
2 Location2 (1)
3 Location3 (1)
can someone show me how to do this?
thanks

You just need group.Count():
var groupedVenueCollection = getTrustActivitiesFromStorage
.GroupBy(customer => customer.venueName)
.OrderBy(g => g.Key);
foreach (var group in groupedVenueCollection)
{
TrustActivities firstActivity = group.First();
filteredVenues.Add(new TrustActivities
{
filterId = Convert.ToInt32(firstActivity.venueId),
filterName = firstActivity.venueName, // or group.Key
filterCount = group.Count() // <--- !!!
});
}
You could also do it in one query without a loop:
List<TrustActivities> filteredVenues = getTrustActivitiesFromStorage
.GroupBy(customer => customer.venueName)
.OrderBy(g => g.Key)
.Select(g => new { Activity = g.First(), Count = g.Count() })
.Select(x => new TrustActivities
{
filterId = Convert.ToInt32(x.Activity.venueId),
filterName = x.Activity.venueName,
filterCount = x.Count
})
.ToList();

Instead of the .Select(g => g.First()), you'd do something like this:
IEnumerable<TrustActivities> groupedVenueCollection = getTrustActivitiesFromStorage
.GroupBy(customer => new { customer.venueId, customer.venueName });
foreach (var activity in groupedVenueCollection)
{
filteredVenues.Add(new TrustActivities
{
filterId = Convert.ToInt32(activity.Key.venueId),
filterName = activity.Key.venueName,
filterCount = activity.Count()
});
}
Also, your variable names are confusing. The table appears to be venues, but you call them customers and activities

LINQ group by sequence and count with sorting

I am searching a best performance method to group and count sequences with sorting using LINQ. I will be processing files even bigger than 500 MBs so performance is most important key in that task.
List<int[]> num2 = new List<int[]>();
num2.Add(new int[] { 35, 44 });
num2.Add(new int[] { 200, 22 });
num2.Add(new int[] { 35, 33 });
num2.Add(new int[] { 35, 44 });
num2.Add(new int[] { 3967, 11 });
num2.Add(new int[] { 200, 22 });
num2.Add(new int[] { 200, 2 });
The result have to be like this:
[35, 44] => 2
[200, 22] => 2
[35, 33] => 1
[35, 44] => 1
[3967, 11] => 1
[200, 2 ] => 1
I have done something like this:
Dictionary<int[], int> result2 = (from i in num2
group i by i into g
orderby g.Count() descending
select new { Key = g.Key, Freq = g.Count() })
.ToDictionary(x => x.Key, x => x.Freq);
SetRichTextBox("\n\n Second grouping\n");
foreach (var i in result2)
{
SetRichTextBox("\nKey: ");
foreach (var r in i.Key)
{
SetRichTextBox(r.ToString() + " ");
}
SetRichTextBox("\n Value: " + i.Value.ToString());
}
But it is not working properly. Any help?

For arrays of length 2, this will work.
num2.GroupBy(a => a[0])
.Select(g => new { A0 = g.Key, A1 = g.GroupBy(a => a[1]) })
.SelectMany(a => a.A1.Select(a1 => new { Pair = new int[] { a.A0, a1.Key }, Count = a1.Count() }));
I think that should give you optimal performance; you could also try an .AsParallel() clause after your first Select statement.
This strategy (grouping successively by the n-th element of the arrays) generalises to arrays of arbitrary length:
var dim = 2;
var tuples = num2.GroupBy(a => a[0])
.Select(g => new Tuple<int[], List<int[]>>(new [] { g.Count(), g.Key }, g.Select(a => a.Skip(1).ToArray()).ToList()));
for (int n = 1; n < dim; n++)
{
tuples = tuples.SelectMany(t => t.Item2.GroupBy(list => list[0])
.Select(g => new Tuple<int[], List<int[]>>(new[] { g.Count() }.Concat(t.Item1.Skip(1)).Concat(new [] { g.Key }).ToArray(), g.Select(a => a.Skip(1).ToArray()).ToList())));
}
var output = tuples.Select(t => new { Arr = string.Join(",", t.Item1.Skip(1)), Count = t.Item1[0] })
.OrderByDescending(o => o.Count)
.ToList();
which generates an output of
Arr = "35, 44", Count = 2
Arr = "200, 22", Count = 2
Arr = "35, 33", Count = 1
Arr = "200, 2", Count = 1
Arr = "3967, 11", Count = 1
in your example. I'll let you test it for higher dimensions. :)
You should be able to parallelise these queries without too much difficulties, as the successive groupings are independent.

You can do something like this:
var results = from x in nums
group x by new { a = x[0], b = x[1] } into g
orderby g.Count() descending
select new
{
Key = g.Key,
Count = g.Count()
};
foreach (var result in results)
Console.WriteLine(String.Format("[{0},{1}]=>{2}", result.Key.a, result.Key.b, result.Count));
The trick is to come up with a way to compare the values in the array, instead of the arrays themselves.
The alternative (and possibly better option) would be to transform your data from int[] to some custom type, override the equality operator on that custom type, then just group x by x into g, but if you're really stuck with int[] then this works.