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Linq - Getting count from unrelated table

How to get to execute a select count(*) from UnrelatedTable where documentLink_Id = x.documentLink_id and add the resulted count to totalTimeAccessed. Both table (PublishedContent and UnrelatedTable have the documentLink_id) in common. Then I would like to select only the rows that have a count greater then 0
var dbData = publishedontext.PublishedContent
.Where(x => x.Status > PublishedStatus.Released)
.OrderBy(x => x.Title)
.Select(x => new DownloadsPerContetnItemReportRows()
{
title = x.Title,
documentLink_Id = x.DocumentLink_Id,
statustatus = x.Status,
totalTimeAccessed = "Select count from an unrelated table"
}

Following code shall work:
totalTimeAccessed = PublishedContent
.Join(UnrelatedTable,pc => pc.DocumentLink_Id,
urt => urt.DocumentLink_Id,(pc,urt) => new {pc,urt})
.Where(y => pc.Count > 0 && urt.Count > 0)
How it Works
Joined PublishedContent with UnrelatedTable on DocumentLink_Id
On the result checked whether Count > 0 for both PublishedContent and UnrelatedTable projections
Would need few modifications based on your specific requirements. In case Count refers to the number of rows not a Column as projected, then Join will anyway give the matching rows, then we don't need the Where clause

Entity Framework - paging with group by skipping group

I have the following query:
var enumerable = repository.Elemtents.Where((s) =>
DbFunctions.TruncateTime(s.Timestamp) <= parameter.To.Date &&
DbFunctions.TruncateTime(s.Timestamp) >= parameter.From.Date)
.OrderByDescending((s) => s.Timestamp)
.GroupBy((s) => new {Date = DbFunctions.TruncateTime(s.Timestamp), s.Timestamp.Hour})
.OrderByDescending((s) => s.Key.Date);
I now want to apply paging with Skip() and Take(). In my table (protocol entries) can be a large amount of data. So I coul do the following, but it would be a perfomance lack.
var result = enumerable
.ToList()
.SelectMany((x) => x)
.Skip(0)
.Take(2);
I want to apply Skip() and Take() on the query directly so that it will be done on the sql server. If I do the following, I get weird results:
var result = repository.Elemtents.Where((s) =>
DbFunctions.TruncateTime(s.Timestamp) <= parameter.To.Date &&
DbFunctions.TruncateTime(s.Timestamp) >= parameter.From.Date)
.OrderByDescending((s) => s.Timestamp)
.GroupBy((s) => new {Date = DbFunctions.TruncateTime(s.Timestamp), s.Timestamp.Hour})
.OrderByDescending((s) => s.Key.Date)
.Skip(0)
.Take(2)
.ToList();
Does anyone know how to resolve this?

Determine Duplicate data using LINQ to EF

I have a dataset that i want to groupby to determine duplicate data.
Example i have a dataset that looks like this.
|id | Number | ContactID
1 1234 5
2 9873 6
3 1234 7
4 9873 6
Now i want to select data that has more than one occurrence of Number but only if the ContactID is not the same.
So basically return
| Number | Count |
1234 2
Any help would be appreciated using LINQ to EF, thanks.

Update:
All thanks to #DrCopyPaste, as he told me that I misunderstood your problem. Here is the correct solution:-
var result = from c in db.list
group c by c.Number into g
let count = g.GroupBy(x => x.ContactID).Where(x => x.Count() == 1).Count()
where count != 0
select new
{
Number = g.Key,
Count = count
};
Sample Fiddle.

This query avoids making a custom IEqualityComparer as if I remember correctly don't think they play well with EF.
var results = data.GroupBy(number => number.Number)
.Where(number => number.Count() > 1)
.Select(number => new
{
Number = number.Key,
Count = number.GroupBy(contactId => contactId.ContactId).Count(x => x.Count() == 1)
})
.Where(x => x.Count > 0).ToList();
Fiddle
It does an initial GroupBy to get all Numbers that are duplicated. It then selects a new type that contains the number and a second GroupBy that groups by ContactId then counts all groups with exactly one entry. Then it takes all results whose count is greater than zero.
Have not testing it against EF, but the query uses only standard Linq operators so EF shouldn't have any issues translating it.

Another way of doing this(using 1 level of grouping):
var results = data
.Where(x => data.Any(y => y.Id != x.Id && y.Number == x.Number && y.ContactId != x.ContactId))
.GroupBy(x => x.Number)
.Select(grp => new { Number = grp.Key, Count = grp.Count() })
.ToList();
Fiddle

Filter some unique Data with LINQ and C#

i am very new with C# and MVC.
My Problem:
I have a list OF IDs
int[] mylist = {10, 23}
I try to query some data from DB
var result = db.tableName.Where(o => mylist.Any(y => y == o.item_ID && o.readed)).ToList();
This is what I get with the query:
item_ID Product_ID readed
277 1232 1
277 1233 1
277 1235 1
280 1235 1
What I need is:
item_ID Product_ID readed
277 1235 1
280 1235 1
If I change "any" to "all" i don't get any results, but I have definitely one item where the condition fits.
I think its more like make a query with id 277, then a query with 280 and then merge the list and return only where where "Product_ID" match.
Any ideas?

I assume that what you need is this:
var temp = db.tableName.Where(o => mylist.Any(y => y == o.item_ID && o.readed))
.ToList();
// Find the Product_id which appeared more than one time
// By the way, this assumes that there is at least one product_Id whihc has appeared more than one time
var neededProductID = temp.GroupBy(x => x.Product_ID)
.Where(x => x.Count() > 1)
.First()
.Key;
// Filter the result by neededProductID
var result = temp.Where(x => x.Product_ID == neededProductID).ToList();
Also, if there could be more tha one Product_ID which has apperaed more than one time, then you can consider this:
var neededProductID = temp.GroupBy(x => x.Product_ID)
.Where(x => x.Count() > 1)
.Select(x => x.Key)
.ToList();
var result = temp.Where(x => neededProductID.Any(y => y == x.Product_ID)).ToList();
By the way, you don't need All(). It tells you if all the elements in a collection match a certain condition.

You can use the following
var result = db.tableName.Where(o => mylist.conains(o.item_ID)
&& o.readed).ToList();

Find MAX/MIN list item using LINQ?

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();