This is my code:
var distinctDateValues = dt.AsEnumerable()
.Select(row => new
{
Date = DateTime.Parse(row.Field<string>("DAY"))
})
.Distinct()
.ToList();
distinctDateValues.Sort(); // getting error on this line
Values in distinctDateValues are:
The error i am getting is "Failed to compare two elements in the array."
Can anybody suggest me as what i am doing wrong here. I want to sort the values in date column of distinctDateValues.
Needless to create anonymous type, in your case the result distinctDateValues is a list of anonymous type, not a list of DateTime, you should get the sorted list of DateTime like below with OrderBy:
var distinctDateValues = dt.AsEnumerable()
.Select(row => row.Field<DateTime>("DAY"))
.Distinct()
.OrderBy(x => x)
.ToList();
Also, you should use built-in method Field<DateTime> instead of using one more step with DateTime.Parse
Just guessing here... your distinctDateValues don't know how to compare themselves... You would need to implement IComparable or something...
Try this:
var distinctDateValues = dt.AsEnumerable()
.Select(row => DateTime.Parse(row.Field<string>("DAY")))
.Distinct()
.ToList();
distinctDateValues.Sort(); // should not get any errors here...
If you really want to create an anonymous type (e.g., you are only showing us a small part of your code), try this:
var distinctDateValues = dt.AsEnumerable()
.Select(row => new
{
Date = DateTime.Parse(row.Field<string>("DAY"))
})
.Distinct()
.OrderBy(d => d.Date) // do the sorting here with linq
.ToList();
Related
I have a linq Query
var tListOfDates = tList.GroupBy(g => g.dateOfSlot)
.Select(s => new {s.Key.Value });
dateOfSlot is a DateTime value
How can I convert tListOfDates to IEnumerable<DateTime>
I've tried top cast the result, but it doesn't work.
You should drop anonymous class new {s.Key.Value } (you don't want it but DateTime):
var tListOfDates = tList
.GroupBy(g => g.dateOfSlot)
.Select(s => s.Key.Value);
It seems that dateOfSlot is of type DateTime?, not DateTime since you put s.Key.Value, not s.Key; if my guess is right you can put it as
var tListOfDates = tList
.Where(item => item.dateOfSlot.HasValue)
.Select(item => item.dateOfSlot.Value)
.Distinct();
A proposition,you take all dates and get the unique date by Distinct
var tListOfDates = tList.Select(g => g.dateOfSlot).Distinct();
I Solved with
IEnumerable<DateTime> tListOfDates = tList.Where(w => w.dateOfSlot.HasValue).Select(g => g.dateOfSlot).Distinct().ToArray().Cast<DateTime>();
May be there is something more that needed and the query can be simplified.
So you have an object tlist, which implements IEnumerable<MySlot>. We don't know a lot of MySlot, yet we know that every MySlot object has a DateTime property DateOfSlot.
The first part of your LINQ statement groups all MySlots in your tlist into groups of MySlots where every MySlot in the group has equal DateOfSlot:
tList.GroupBy(mySlot => mySlot.dateOfSlot)
Every group has a Key which contains this common DateOfSlot. So the Key is d DateTime object
The second part projects every group into one element:
.Select(group => new {group.Key.Value });
group.Key is a DateTime. The problem is that a Datetime does not have a property Value. Are you sure that DateOfSlot is a DateTime?
It's not entirely certain what you want.
I have an IEnumerable<MySlot> in tList, and I want all used DateOfSlot values in this list
var allUsedDateOfSlotValues = tList.Select(mySlot => mySlot.DateOfSlot);
But now I have duplicates, I don't want duplicates!
var allDistinctUsedDateOfSlotValues = tList
.Select(mySlot => mySlot.DateOfSlot)
.Distinct();
This will have the same result as your code:
var result = tList.GroupBy(mySlot => mySlot.DateOfSlot)
// result: groups of mySlots with same DateOfSlot
.Select(group => group.Key)
// result: distinct values of DateOfSlot
I am trying to convert the result of the query into IDictionary
Here string will contain orderId and the int will contain the TradedQuantity
The query below should join three objects Order, OrderRevision and OrderEvent.
1 Order can have many orderRevisions
1 OrderRevision can have many orderEvents
What the query is trying to do is to inner join three objects and get all order objects whose order id matches the list of orderids supplied to it. Then it does a group by based on orderId and gets the latest TradedQuantity from orderEvents object. LatestTradedQuantity will be the TradedQuantityFrom latest OrderEvent. For now the latest orderevent can be regarded as the one that has highest OrderEventId value.
OrderRevision revisionAlias = null;
Order orderAlias = null;
var query =
Session.QueryOver<OrderEvent>()
.JoinAlias(oe => oe.OrderRevision,() => revisionAlias)
.JoinAlias(oe => oe.OrderRevision.Order,() => orderAlias)
.Where(x => x.OrderRevision.Order.SourceSystem.Name.ToLower() == sourceSystem.ToLower())
.WhereRestrictionOn(x => x.OrderRevision.Order.Id).IsIn(orderIds.ToList())
.SelectList(list => list.SelectGroup(x => x.OrderRevision.Order.SourceOrderIdentifier)
.SelectMax(x => x.Id).Select(x => x.TradedQuantity))
.Select(x => new KeyValuePair<string, int?>(x.OrderRevision.Order.SourceOrderIdentifier, x.TradedQuantity)
);
As this query does not do what is supposed to. Could you please help and let me know how the result can be cast into IDictionary?
You have tagged your question with linq-to-nhibernate, so I guess using it instead of queryover would suit you. With Linq, use a sub-query for selecting the "max" order events ids for each order, then query them and project them to a dictionary.
using System.Linq;
using NHibernate.Linq;
...
var orderEventsIdsQuery = Session.Query<OrderEvent>()
.Where(oe => orderIds.Contains(oe.OrderRevision.Order.Id))
.GroupBy(oe => oe.OrderRevision.Order.SourceOrderIdentifier,
(soi, oes) => oes.Max(oe => oe.Id));
var result = Session.Query<OrderEvent>()
.Where(oe => orderEventsIdsQuery.Contains(oe.Id))
.ToDictionary(oe => oe.OrderRevision.Order.SourceOrderIdentifier,
oe => oe.TradedQuantity);
This should do the job. I do not use QueryOver and I will not try to give an answer for doing it with QueryOver.
I am trying to sort the contents of a CSV file according to their dates with the following code from a question a posted earlier:
private class CSVEntry
{
public DateTime Date { get; set; }
public string Grp { get; set; }
}
...
List<CSVEntry> csvList = new List<CSVEntry>();
csvList.Add(new CSVEntry() { Date = DateTime.ParseExact(col[7], "dd/MM/yyyy", null), Grp = col[9] });
var results = csvList.OrderBy(x => x.Date); // An error occurs at "Date".
...
But I got this error:
'string' does not contain a definition for 'Date' and no extension method 'Date' accepting a first argument of type 'string' could be found.
What I want the output to be is the strings from other columns but sorted chronologically. When I tried using this code to display the dates:
var results = csvList.Where(x => x.Grp == "DEFAULT").OrderBy(x => x.Date);
It works perfectly with the output as dates sorted chronologically. However, this time I don't want to display the dates. I want to display the strings from other columns like I've mentioned above. I tried using
var results = csvList.Select(x => x.Grp).OrderBy(x => x.Date);
but got the same error as well. Where have I gone wrong? I am new to LINQ and unfamiliar with List<T> and IEnumerable<T> and this is my first time using them.
Add Select after your order the records, Like below
var results = csvList
.Where(x => x.Grp == "DEFAULT")
.OrderBy(x => x.Date)
.Select(x => x.Grp);
Reddy's answer should work, but I will explain it for you, so you understand why it does.
When you use the Select(x => x.Grp) Statement you don't have a IEnumerable<CSVEntry> anymore. You only have a IEnumerable with all Grp-Entrys from your csvList. So When you try to order them by Date by adding a OrderBy(x => x.Date) Statement, Linq doesn't know the Date Property, because in this Statement x is only a string, not a CsvEntry.
In Reddys Answer, he first filter all Entrys by Grp == "DEFAULT". After that he has a IEnumerable<CsvEntry> left, so he can Order them by x.Date. After that, again, he has a IEnumerable<CsvEntry> left. Only after the last Statement, the Select(x => x.Grp) Statement, he has a IEnumerable<string> left.
Hope that helps :)
I have a list of objects that have a string, and int and another int.
I want to be able to create a list of all the objects that have a duplicate string.
Here is what I have so far:
MyObject duplicates = allMyObjects.GroupBy(a => a.MyString)
.Where(a => a.Count() > 1)
.ToList();
The error I am getting is that I cannot implicitly convert the type System.Collections.Generic.List<string, MyObject> to MyObject
var duplicates = allMyObjects.GroupBy(a => a.MyString)
.Where(a => a.Count() > 1)
.SelectMany(g=>g)
.ToList();
you need to write
List<MyObject> duplicates = allMyObjects.GroupBy(a => a.MyString)
.Where(a => a.Count() > 1)
.ToList();
You could use ToLookup to make a nice data structure with all the info you need
var objectsByString = allMyObjects.ToLookup(o => o.MyString);
This will return a Lookup<string, MyObject>. You can get the duplicate strings using:
var duplicateStrings = objectsByString.Where(l => l.Count()>1).Select(l => l.Key);
which will return a IEnumerable<string> with the duplicate strings. And, for each duplicate you can access the actual objects that have duplicates using something like this:
string duplicateKey = duplicateStrings.First();
var duplicateObjects = objectsByString[duplicateKey]
which returns a IEnumerable<MyObject> with the items that have that string.
There are several problem, the first is a List-of-MyObject cannot be assigned to MyObject, so let's use var to ignore this for a second.
var duplicates = allMyObjects.GroupBy(a => a.MyString)
.Where(a => a.Count() > 1)
.ToList();
Now, the type of duplicates is List<IGrouping<string, MyObject>> (despite the incorrectly reported error message). Whoops, gotta get rid of (or write to code to account for) the groups!
var duplicates = allMyObjects.GroupBy(a => a.MyString)
.Where(a => a.Count() > 1)
.SelectMany(g => g)
.ToList();
Now the type of duplicates is List<MyObject>, after having selected every ("selected many") object from every group with more than one item. Better, but this still isn't an MyObject. Well, that's fine: fix the declared type of the variable (that var was previously automatically doing)..
List<MyObject> duplicates = /* same as before */;
Or leave var to do it's thing and if an IEnumerable<MyObject> is fine, simply omit the ToList:
var duplicates = allMyObjects.GroupBy(a => a.MyString)
.Where(a => a.Count() > 1)
.SelectMany(g => g);
Go forth and iterate thy duplicates!
I've a problem in my C# application... I've some school classes in database for example 8-B, 9-A, 10-C, 11-C and so on .... when I use order by clause to sort them, the string comparison gives results as
10-C
11-C
8-B
9-A
but I want integer sorting on the basis of first integer present in string...
i.e.
8-B
9-A
10-C
11-C
hope you'll understand...
I've tried this but it throws exception
var query = cx.Classes.Select(x=>x.Name)
.OrderBy( x=> new string(x.TakeWhile(char.IsDigit).ToArray()));
Please help me... want ordering on the basis of classes ....
Maybe Split will do?
.OrderBy(x => Convert.ToInt32(x.Split('-')[0]))
.ThenBy(x => x.Split('-')[1])
If the input is well-formed enough, this would do:
var maxLen = cx.Classes.Max(x => x.Name.Length);
var query = cx.Classes.Select(x => x.Name).OrderBy(x => x.PadLeft(maxLen));
You can add 0 as left padding for a specified length as your data for example 6
.OrderBy(x => x.PadLeft(6, '0'))
This is fundamentally the same approach as Andrius's answer, written out more explicitly:
var names = new[] { "10-C", "8-B", "9-A", "11-C" };
var sortedNames =
(from name in names
let parts = name.Split('-')
select new {
fullName = name,
number = Convert.ToInt32(parts[0]),
letter = parts[1]
})
.OrderBy(x => x.number)
.ThenBy(x => x.letter)
.Select(x => x.fullName);
It's my naive assumption that this would be more efficient because the Split is only processed once in the initial select rather than in both OrderBy and ThenBy, but for all I know the extra "layers" of LINQ may outweigh any gains from that.