I have a list Having multiple Items and 3 props ID,DATE,COMMENT.ID field is Auto incremented in DATABASE.
Let say list Contains
2,16AUG,CommentMODIFIED
1,15AUG,CommentFIRST
3,18AUG,CommentLASTModified
I want to get a single ITEM.Item Having Minimum DATE and having Latest Comment. In this case
1,15AUG,CommentLASTModified
Any easy way to do it using LINQ.
orderedItems = items.OrderBy(x => x.Date);
var result = items.First();
result.Comment = items.Last().Comment;
To get a single item out of the list, you can order the items then take the first one, like this:
var result = items
.OrderByDescending(x => x.Date)
.First();
But First will throw an exception if the items collection is empty. This is a bit safer:
var result = items
.OrderByDescending(x => x.Date)
.FirstOrDefault();
To get the min / max of different columns you can do this:
var result =
new Item {
Id = 1,
Date = items.Min(x => x.Date),
Comment = items.Max(x => x.Comment)
};
But this will require two trips to the database. This might be a bit more efficient:
var result =
(from x in items
group x by 1 into g
select new Item {
Id = 1,
Date = g.Min(g => g.Date),
Comment = g.Max(g => g.Comment)
})
.First();
Or in fluent syntax:
var result = items
.GroupBy(x => 1)
.Select(g => new Item {
Id = 1,
Date = g.Min(g => g.Date),
Comment = g.Max(g => g.Comment)
})
.First();
Related
What I am trying to do is get the top 10 most sold Vegetables by grouping them by an Id passed by parameter in a function and ordering them by the sum of their Quantity. I don't know how to use SUM or (total) quite yet but I thought I'd post it here seeking help. If you need me offering you anything else I will be ready.
This is my code:
TheVegLinQDataContext db = new TheVegLinQDataContext();
var query =db.OrderDetails.GroupBy(p => p.VegID)
.Select(g => g.OrderByDescending(p => p.Quantity)
.FirstOrDefault()).Take(10);
And this is an image of my database diagram
Group orders by Vegetable ID, then from each group select data you want and total quantity:
var query = db.OrderDetails
.GroupBy(od => od.VegID)
.Select(g => new {
VegID = g.Key,
Vegetable = g.First().Vegetable, // if you have navigation property
Total = g.Sum(od => od.Quantity)
})
.OrderByDescending(x => x.Total)
.Select(x => x.Vegetable) // remove if you want totals
.Take(10);
Since this is not clear that you are passing what type of id as function parameter, I'm assuming you are passing orderId as parameter.
First apply where conditions then group the result set after that order by Total sold Quantity then apply Take
LINQ query
var result = (from a in orderdetails
where a.OrderId == orderId //apply where condition as per your needs
group a by new { a.VegId } into group1
select new
{
group1.Key.VegId,
TotalQuantity = group1.Sum(x => x.Quantity),
group1.FirstOrDefault().Vegitable
}).OrderByDescending(a => a.TotalQuantity).Take(10);
Lamda (Method) Syntax
var result1 = orderdetails
//.Where(a => a.OrderId == 1) or just remove where if you don't need to filter
.GroupBy(x => x.VegId)
.Select(x => new
{
VegId = x.Key,
x.FirstOrDefault().Vegitable,
TotalQuantity = x.Sum(a => a.Quantity)
}).OrderByDescending(x => x.TotalQuantity).Take(10);
var entity = await _abcRepository.get(Id);
var X = entity.GroupBy(c => c.number).Where(grp => grp.Count() == 1).Take(10).ToList();
in images you see [0] and inside of it one more [0].
How can I get that model value.
X[0][0] is not working.
X.Value is not working.
I need to convert that dictionary to model.
Use .Select to normalize aggregation as per your wish.
var X = entity.GroupBy(c => c.number).Where(grp => grp.Count() == 1)
.Select(group => new { GroupKey = group.Key, Items = group.ToList() })
.Take(10).ToList();
You could try something like this:
var entity = await _abcRepository.get(Id);
var results = entity.GroupBy(c => c.number)
.Where(grp => grp.Count() == 1)
.Take(10)
.ToDictionary(grp => grp.Key, grp => grp.First());
Essentially, the lambda you pass in Where method certifies that the groups are created contains only one item. That being said, you can use the First on each group to fetch that one element.
How do you perform multiple seperate aggregations on different grouping in linq?
for example, i have a table:
UNO YOS Ranking Score
123456 1 42 17
645123 3 84 20
I want to perform an set of aggregations on this data both grouped and ungrouped, like:
var grouped = table.GroupBy(x => x.score )
.Select(x => new
{
Score = x.Key.ToString(),
OverallAverageRank = x.Average(y => y.Ranking),
Year1RankAvg = x.Where(y => y.YOS == 1).Average(y => y.Ranking),
Year2RankAvg = x.Where(y => y.YOS == 2).Average(y => y.Ranking)
//...etc
});
I also want to perform different aggregations (standard deviation) on the same slices and whole-set data.
I can't figure out how to both group and not group the YOS at the same time and while this compiles fine, when it comes to runtime, I get "Sequence contains no elements", if any of the YOS averages are in.
Like anything programming, when you have a sequence of similar items, use a collection. In this case, I left it IEnumerable, but you could make it a List, or a Dictionary by YOS, if desired.
var ans = table.GroupBy(t => t.Score)
.Select(tg => new {
Score = tg.Key,
OverallAverageRank = tg.Average(t => t.Ranking),
YearRankAvgs = tg.GroupBy(t => t.YOS).Select(tyg => new { YOS = tyg.Key, RankAvg = tyg.Average(t => t.Ranking) })
});
If you need the range of years from 1 to max (or some other number) filled in, you can modify the answer:
var ans2 = ans.Select(soryr => new {
soryr.Score,
soryr.OverallAverageRank,
YearRankDict = soryr.YearRankAvgs.ToDictionary(yr => yr.YOS),
YearMax = soryr.YearRankAvgs.Max(yr => yr.YOS)
})
.Select(soryr => new {
Score = soryr.Score,
OverAverageRank = soryr.OverallAverageRank,
YearRankAvgs = Enumerable.Range(1, soryr.YearMax).Select(yos => soryr.YearRankDict.ContainsKey(yos) ? soryr.YearRankDict[yos] : new { YOS = yos, RankAvg = 0.0 }).ToList()
});
If you preferred, you could modify the original ans to return RankAvg as double? and put null in place of 0.0 when adding missing years.
I have a class (ApplicationHistory) with 3 properties:
ApplicantId, ProviderId, ApplicationDate
I return the data from the database into a list, however this contains duplicate ApplicantId/ProviderId keys.
I want to supress the list so that the list only contains the the earliest Application Date for each ApplicantId/ProviderId.
The example below is where I'm currently at, but I'm not sure how to ensure the earliest date is returned.
var supressed = history
.GroupBy(x => new
{
ApplicantId = x.ApplicantId,
ProviderId = x.ProviderId
})
.First();
All advice appreciated.
Recall that each group formed by the GroupBy call is an IGrouping<ApplicationHistory>, which implements IEnumerable<ApplicationHistory>. Read more about IGrouping here. You can order those and pick the first one:
var oldestPerGroup = history
.GroupBy(x => new
{
ApplicantId = x.ApplicantId,
ProviderId = x.ProviderId
})
.Select(g => g.OrderBy(x => x.ApplicationDate).FirstOrDefault());
You are selecting first group. Instead select first item from each group:
var supressed = history
.GroupBy(x => new {
ApplicantId = x.ApplicantId,
ProviderId = x.ProviderId
})
.Select(g => g.OrderBy(x => x.ApplicationDate).First());
Or query syntax (btw you don't need to specify names for anonymous object properties in this case):
var supressed = from h in history
group h by new {
h.ApplicantId,
h.ProviderId
} into g
select g.OrderBy(x => x.ApplicationDate).First();
I am currently using Linq to retrieve a list of distinct values from my data table. I am then looping through the list and again calling a linq query to retrieve a list of values for each
value in the first list.
_keyList = new SortedList<int, List<int>>();
var AUGroupList = ProcessSummaryData.AsEnumerable()
.Select(x => x.Field<int>("AUGroupID"))
.Distinct()
.ToList<int>();
foreach (var au in AUGroupList)
{
var AUList = ProcessSummaryData.AsEnumerable()
.Where(x => x.Field<int>("AUGroupID") == au)
.Select(x => x.Field<int>("ActivityUnitID"))
.ToList<int>();
_keyList.Add(au, AUList);
}
I am then adding the value to a sorted list along with the corresponding second list.
How can I combine the above two queries into one Linq query so that I don't have to call them separately?
You should be able to do something like:
var groupQuery = from d in ProcessSummary.AsEnumerable()
group d by new { Key = d.Field<int>("AUGroupID") } into g
select new { GroupID = g.Key, Values = g.Distinct().ToList() };
Then you can loop through the groupQuery and populate the sorted list. The Key property will contain the group id, and the Values property will have a distinct list of values.
Have you tried this?
var _keyList = new SortedList<int, List<int>>();
var AUGroupList = ProcessSummaryData.AsEnumerable()
.Select(x => x.Field<int>("AUGroupID"))
.Distinct()
.Where(x => x.Field<int>("AUGroupID") == au)
.Select(x => x.Field<int>("ActivityUnitID"))
.ToList<int>();
_keyList.Add(au, AUList);
}
Your provider should cope with that, if not there's a few other ways.