I have the following block of code which works fine;
var boughtItemsToday = (from DBControl.MoneySpent
bought in BoughtItemDB.BoughtItems
select bought);
BoughtItems = new ObservableCollection<DBControl.MoneySpent>(boughtItemsToday);
It returns data from my MoneySpent table which includes ItemCategory, ItemAmount, ItemDateTime.
I want to change it to group by ItemCategory and ItemAmount so I can see where I am spending most of my money, so I created a GroupBy query, and ended up with this;
var finalQuery = boughtItemsToday.AsQueryable().GroupBy(category => category.ItemCategory);
BoughtItems = new ObservableCollection<DBControl.MoneySpent>(finalQuery);
Which gives me 2 errors;
Error 1 The best overloaded method match for 'System.Collections.ObjectModel.ObservableCollection.ObservableCollection(System.Collections.Generic.List)' has some invalid arguments
Error 2 Argument 1: cannot convert from 'System.Linq.IQueryable>' to 'System.Collections.Generic.List'
And this is where I'm stuck! How can I use the GroupBy and Sum aggregate function to get a list of my categories and the associated spend in 1 LINQ query?!
Any help/suggestions gratefully received.
Mark
.GroupBy(category => category.ItemCategory); returns an enumerable of IGrouping objects, where the key of each IGrouping is a distinct ItemCategory value, and the value is a list of MoneySpent objects. So, you won't be able to simply drop these groupings into an ObservableCollection as you're currently doing.
Instead, you probably want to Select each grouped result into a new MoneySpent object:
var finalQuery = boughtItemsToday
.GroupBy(category => category.ItemCategory)
.Select(grouping => new MoneySpent { ItemCategory = grouping.Key, ItemAmount = grouping.Sum(moneySpent => moneySpent.ItemAmount);
BoughtItems = new ObservableCollection<DBControl.MoneySpent>(finalQuery);
You can project each group to an anyonymous (or better yet create a new type for this) class with the properties you want:
var finalQuery = boughtItemsToday.GroupBy(category => category.ItemCategory);
.Select(g => new
{
ItemCategory = g.Key,
Cost = g.Sum(x => x.ItemAmount)
});
The AsQueryable() should not be needed at all since boughtItemsToday is an IQuerable anyway. You can also just combine the queries:
var finalQuery = BoughtItemDB.BoughtItems
.GroupBy(item => item.ItemCategory);
.Select(g => new
{
ItemCategory = g.Key,
Cost = g.Sum(x => x.ItemAmount)
});
Related
I have a datatable like this:
I want to group this table For FIELD A and FIELD B,
and the third field of my group should be lists of FIELD C, but it must be grouped by ID field.
At the end, the result should be like this:
First Field | Second Field | Third Field
------------+--------------+----------------
5 | XXXX |(8) (2,6,3) (9)
5 | KKKK |(8,3)
The third field must be a list of lists.
How can i do this with LINQ?
I tried this so far:
var trytogroup = (from p in datatable.AsEnumerable()
group p by new
{
ID = p["Id"].ToLong(),
FieldA = p["FieldA"].ToLong(),
FieldB = p["FieldB"].ToString()
} into g
select new
{
FirstField = g.Key.FieldA,
SecondField = g.Key.FieldB,
ThirdField = datatable.AsEnumerable().Where(p => p["FieldA"].ToLong() == g.Key.FieldA && p["FieldB"].ToString() == g.Key.FieldB).Select(p => p["FieldC"].ToLong()).GroupBy(x => x["Id"].ToLong()).Distinct().ToList()
});
What's wrong with your query:
You don't need to group by three fields on first place. Grouping by ID should be done within group which you have by FieldA and FieldB
When getting ThirdField you don't need to query datatable again - you already have all required data. You just need to add grouping by ID
Correct query:
from r in datatable.AsEnumerable()
group r by new {
FieldA = r.Field<long>("FieldA"),
FieldB = r.Field<string>("FieldB")
} into g
select new
{
First = g.Key.FieldA,
Second = g.Key.FieldB,
Third = g.GroupBy(r => r.Field<long>("ID"))
.Select(idGroup => idGroup.Select(i => i.Field<long>("FieldC")).ToList())
}
If you prefere lambdas, your query could look like:
dataSource
.GroupBy(item => new { item.FieldA, item.FieldB })
.Select(group => new
{
First = group.Key.FieldA,
Second = group.Key.FieldB,
Third = group.GroupBy(q => q.Id).Select(q => q.Select(e => e.FieldC).ToArray()).ToArray()
}).ToArray();
Just few small notes. .GroupBy uses Lookup to get the Groupings, so some overhead can be avoided by replacing .GroupBy( with .ToLookup( when deffered execution is not needed.
The elements in each Grouping are stored in array, so I don't see much use in converting them .ToList (but you can save a bit of space if you convert them .ToArray).
DataTable.AsEnumerable uses .Rows.Cast<TRow>(), but also seems to do some extra stuff when there is any DataView sorting or filtering that are usually not needed.
var groups = datatable.Rows.Cast<DataRow>()
.ToLookup(r => Tuple.Create(
r["FieldA"] as long?,
r["FieldB"]?.ToString()
))
.Select(g => Tuple.Create(
g.Key.Item1,
g.Key.Item2,
g.ToLookup(r => r["ID"] as long?, r => r["FieldC"] as long?)
)).ToList();
As usual, premature optimization is the root of all evil but I thought the information might be useful.
I have a some code to sort my collection in linq in C#. I want it to group by the houseName to sum over the volumes, order that collection, but also pass a third parameter, pctVol, to the new sorted collection. What am I doing wrong? I know that the problem lies in the pctVol = group.Selecct(item => item.pctVol) line.
var inBetween = this.GroupBy(item => item.houseName)
.Select(group =>
new DataItem
{
houseName = group.Key,
VOLUME = group.Sum(item => item.VOLUME),
pctVol = group.Select(item => item.pctVol)
})
.ToList();
ObservableCollection<DataItem> objSort = new ObservableCollection<DataItem>(inBetween.OrderBy(DataItem =>
DataItem.VOLUME));
return objSort;
What kind of value do you want pctVol to have? With that code, it looks like DataItem.pctVol will be an IEnumerable containing all the pctVol values in that group.
If you want a single value, and all the pctVol values in each group are guaranteed to be the same, then you could just take the value from the first element, like this: pctVol = group.First().pctVol
SELECT
[TimeStampDate]
,[User]
,count(*) as [Usage]
FROM [EFDP_Dev].[Admin].[AuditLog]
WHERE [target] = '995fc819-954a-49af-b056-387e11a8875d'
GROUP BY [Target], [User] ,[TimeStampDate]
ORDER BY [Target]
My database table has the columns User, TimeStampDate, and Target (which is a GUID).
I want to retrieve all items for each date for each user and display count of entries.
The above SQL query works. How can I convert it into LINQ to SQL? Am using EF 6.1 and my entity class in C# has all the above columns.
Create Filter basically returns an IQueryable of the entire AuditLogSet :
using (var filter = auditLogRepository.CreateFilter())
{
var query = filter.All
.Where(it => it.Target == '995fc819-954a-49af-b056-387e11a8875d')
.GroupBy(i => i.Target, i => i.User, i => i.TimeStamp);
audits = query.ToList();
}
Am not being allowed to group by on 3 columns in LINQ and I am also not sure how to select like the above SQL query with count. Fairly new to LINQ.
You need to specify the group by columns in an anonymous type like this:-
var query = filter.All
.Where(it => it.Target == '995fc819-954a-49af-b056-387e11a8875d')
.GroupBy(x => new { x.User, x.TimeStampDate })
.Select(x => new
{
TimeStampDate= x.Key.TimeStampDate,
User = x.Key.User,
Usage = x.Count()
}).ToList();
Many people find query syntax simpler and easier to read (this might not be the case, I don't know), here's the query syntax version anyway.
var res=(from it in filter.All
where it.Target=="995fc819-954a-49af-b056-387e11a8875d"
group it by new {it.Target, it.User, it.TimeStampDate} into g
orderby g.Key.Target
select new
{
TimeStampDate= g.Key.TimeStampDate,
User=g.Key.User,
Usage=g.Count()
});
EDIT: By the way you don't need to group by Target neither OrderBy, since is already filtered, I'm leaving the exact translation of the query though.
To use GroupBy you need to create an anonymous object like this:
filter.All
.Where(it => it.Target == '995fc819-954a-49af-b056-387e11a8875d')
.GroupBy(i => new { i.Target, i.User, i.TimeStamp });
It is unnecessary to group by target in your original SQL.
filter.All.Where( d => d.Target == "995fc819-954a-49af-b056-387e11a8875d")
.GroupBy(d => new {d.User ,d.TimeStampDate} )
.Select(d => new {
User = d.Key.User,
TimeStampDate = d.Key.TimeStampDate,
Usage = d.Count()
} );
I have a class and its List
abc cs = new abc();
List<abc> Lst_CS = new List<abc>();
and I set some value by HidenField in foreach loop
foreach (blah blah)
{
cs = new abc{
No = VKNT,
GuidID=hdnGuidID.Value.ToString(),
RecID=hdnRecID.Value.ToString(),
Date=HdnDate.Value.ToString()
};
Lst_CS.Add(cs);
}
and finally I get a List_CS and I order by Lst_CS according to Date like this;
IEnumerable<abc> query = Lst_CS.OrderBy(l => l.Date).ToList();
but in extra, I want to group by according to No.
Briefly, I want to order by Date and then group by No on Lst_CS How can I do ?
Thanks for your answer
Well you just just do the ordering then the grouping like so:
Lst_CS.OrderBy(l => l.Date)
.GroupBy(l => l.No)
.ToList();
Each list of items in each group will be ordered by date. The groupings will be in the order that they are found when the entire list is ordered by date.
Also your ForEach can be done in one Linq statement, then combined with the ordering and grouping:
var query = blah.Select(b => new abc{
No = VKNT,
GuidID=hdnGuidID.Value.ToString(),
RecID=hdnRecID.Value.ToString(),
Date=HdnDate.Value.ToString()
})
.OrderBy(l => l.Date)
.GroupBy(l => l.No)
.ToList();
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();