I have this Linq statement:
List<string> phoneNumbers = from t
in fixedLineData
select t.phoneNumber.Distinct();
Basically what I want is a distinct list of strings sent back from the LINQ query.
Is this possible?
Make it
var phoneNumbers =
(from t in fixedLineData
select t.phoneNumber)
.Distinct().ToList();
But you might as well skip the query-syntax:
var phoneNumbers =
fixedLineData
.Select (t => t.phoneNumber)
.Distinct()
.ToList();
The .ToList() will make the resulting type IList<string>
Related
The code below userModel.Carriers is the type of IEnumerable<CarrierModel>.
userModel.Carriers has a list of carriers having Ids. With those Ids, I want to get CarrierDivision usign linq. But, I can't get it right because linq sqlexpression is not compatible with IEnumerable expression.
userModel.Carriers = carriersForRegion.Select(carrier => Mapper.Map<CarrierModel>(carrier))
.ToList();
var carrierDivision = from c in db.CarrierDivision where c.Contains();
collection.Contains will generate .. WHERE CarrierId IN (1, 2, 3) sql query
var carrierIds = userModel.Carriers.Select(carrier => carrier.Id).ToArray();
var divisions = db.CarrierDivision
.Where(division => carrierIds.Contains(division.CarrierId))
.ToArray();
In case db.CarrierDivision returns IEnumerable(not database), then I would suggest to create HashSet of carrier ids.
var carrierIds = userModel.Carriers.Select(carrier => carrier.Id).ToHashSet();
var divisions = db.CarrierDivision
.Where(division => carrierIds.Contains(division.CarrierId))
.ToArray();
With HashSet search executed without extra enumerations - O(1)
I have two tables..
Student (StudentId,Name,FatherName)
Qualification (QualificationId,StudentId,DegreeName)
I have got data like this..
var myList = (from c in entities.Students
join q in entities.Qualifications on c.StudentId equals q.StudentId
select new {c.Name,c.FatherName,q.DegreeName}).ToList();
Now i want to filter myList more.. How can i do it, like..
var filteredList = myList.Select(c=> new Student
{
Name=c.Name,
FatherName=c.FatherName
//Degree=C.Degree
}).ToList();
The above Linq Query is not working if i want to get DegreeName also, My Question is how to further Filter myList.
Thanks.
var filteredList = myList.Where(i => i.FatherName == "Shahid").ToList();
Keep in mind since you called ToList() on the original query you are now filtering in memory. If you want to filter in the database then remove the ToList() on the first query and do it like this:
var myList = from c in entities.Students
join q in entities.Qualifications on c.StudentId equals q.StudentId
select new {
c.Name,
c.FatherName,
q.DegreeName
};
var filteredInDatabase = myList.Where(i => i.FatherName == "Shahid").ToList();
I am trying to write a linq query that will only return certain columns from my entity object into a list object.
Below is my code which produces an error(can't implicitly convert a generic list of anonymous types to a generic list of type TBLPROMOTION):
IQueryable<TBLPROMOTION> matches = webStoreContext.TBLPROMOTION.Include("TBLSTORE").Include("LKPROMOTIONTYPE");
List<TBLPROMOTION> promotionInfo = null;
promotionInfo = (from p in matches
orderby p.PROMOTION_NM descending
select new { p.EFFECTIVE_DT, p.EXPIRE_DT, p.IS_ACTIVE,
p.PROMOTION_DESC, p.PROMOTION_ID, p.PROMOTION_NM }).ToList();
What would be the best way to accomplish this. I do not want to do a "select p" in this case and return all the columns associated with the query.
thanks in advance,
Billy
Can't you do var promotionInfo = () and get a list of anonymous types?
Okay, basically you can not cast an Anonymous type to a known type like TBLPROMOTION.
ofcourse, you can say var promotionInfo = and then get an IEnumerable<{Anonymoustype}> and use that to do, what you were wanting to do with promotionInfo.
Also, personally I prefer the Fluent version of a linq query, easy on the eyes, good programming diet, at least for me :)
var promotionInfo = matches
.OrderByDescending( p => p.PROMOTION_NM)
.Select( p => new { p.EFFECTIVE_DT,
p.EXPIRE_DT,
p.IS_ACTIVE,
p.PROMOTION_DESC,
p.PROMOTION_ID,
p.PROMOTION_NM})
.ToList();
If you're moving from a L2E query to a Type already defined, you may need a step between. I haven't tried to compile this but something like:
List<TBLPROMOTION> promotions = new List<TBLPROMOTION>();
var results = from p in matches
orderby p.PROMOTION_NM descending
select new
{
p.EFFECTIVE_DT,
p.EXPIRE_DT,
p.IS_ACTIVE,
p.PROMOTION_DESC,
p.PROMOTION_ID,
p.PROMOTION_NM
};
foreach (var v in results)
{
promotions.Add(new TBLPROMOTION(v.EFFECTIVE_DT, v.EXPIRE_DT, v.IS_ACTIVE,
v.PROMOTION_DESC, v.PROMOTION_ID, v.PROMOTION_NM));
}
Based on the comment below, you might try something like:
foreach(var v in results)
{
TBLPROMOTION temp = new TBLPROMOTION();
temp.EFFECTIVE_DT = v.EFFECTIVE_DT;
temp.EXPIRE_DT = v.EXPIRE_DT;
temp.IS_ACTIVE = v.IS_ACTIVE
// Assign Other Properties
promotions.Add(temp);
}
.......
Sorry: Just read the addition to the top.
Are you sure that none of the fields you're leaving out (instead of saying "select p") are required for a TBLPROMOTION object? Also, sense your TBLPROMOTION object is going to have properties (and therefore memory allocated) for those skipped fields, why not just use an annonymous type or set up a helper class that contains only your needed properties?
#Billy, following code worked for me.
List<TBLPROMOTION> promotionInfo =
(from p in matches
orderby p.PROMOTION_NM descending
select new TBLPROMOTION(p.EFFECTIVE_DT, p.EXPIRE_DT, p.IS_ACTIVE,
p.PROMOTION_DESC, p.PROMOTION_ID, p.PROMOTION_NM)
).ToList();
did you try
select new TBLPROMOTION {.....
instead of
select new {.....
List<TBLPROMOTION> promotionInfo = null;
promotionInfo = (from p in matches
orderby p.PROMOTION_NM descending
select new TBLPROMOTION { COL1 = p.EFFECTIVE_DT, COL2 = p.EXPIRE_DT, COL3 = p.IS_ACTIVE... }).ToList();
Where COL1, COL2, ... are the names of the properties on TBLPROMOTION you wish you populate.
If you want a subset of the table you have 2 options:
#Fredou mentioned select new TBLPROMOTION{...}
other way is to create a custom DTO which has the exact properties & select them instead like:
List promotionInfo = ...
select new TBLPROMOTION_DTO{
Effective_dt = ...
}
HTH
I have a LINQ query that returns some object like this...
var query = from c in db.Customers
where ...
select c;
Then I do this
List<String> list = new List<String>();
foreach (ProgramLanguage c in query)
{
//GetUL returns a String
list.Add(GetUL(c.Property,c.Property2));
}
Is there a way to combine into something list this?
var query = from c in db.Customers
where ...
select new
{
GetUL(c.Property,c.Property2)
}).ToList<String>();
This query should do both steps in one fell swoop.
var list = db.Customers.Where(c => ...).
Select(c => GetUL(c.Property,c.Property2)).ToList()
*Note, I prefer this LINQ syntax over the other version.
var query = db.Customers.Where(c => ...)
.Select(c => GetUL(c.Property, c.Property2))
.ToList();
or in query syntax if you prefer
var query = (from c in db.Customers
where ...
select GetUL(c.Property, c.Property2)).ToList();
var slist = (from c in db.Customers
where ...
select new
{
GetUL(c.Property,c.Property2)
}).ToList();
Also, if you haven't already I highly recommend downloading and using LinqPad. It's a killer little app that lets you experiment with linq queries (and so much more!)
I know in normal Linq grammar, orderby xxx descending is very easy, but how do I do this in Lambda expression?
As Brannon says, it's OrderByDescending and ThenByDescending:
var query = from person in people
orderby person.Name descending, person.Age descending
select person.Name;
is equivalent to:
var query = people.OrderByDescending(person => person.Name)
.ThenByDescending(person => person.Age)
.Select(person => person.Name);
Use System.Linq.Enumerable.OrderByDescending()?
For example:
var items = someEnumerable.OrderByDescending();
Try this:
List<int> list = new List<int>();
list.Add(1);
list.Add(5);
list.Add(4);
list.Add(3);
list.Add(2);
foreach (var item in list.OrderByDescending(x => x))
{
Console.WriteLine(item);
}
Try this another way:
var qry = Employees
.OrderByDescending (s => s.EmpFName)
.ThenBy (s => s.Address)
.Select (s => s.EmpCode);
Queryable.ThenBy
This only works in situations where you have a numeric field, but you can put a minus sign in front of the field name like so:
reportingNameGroups = reportingNameGroups.OrderBy(x=> - x.GroupNodeId);
However this works a little bit different than OrderByDescending when you have are running it on an int? or double? or decimal? fields.
What will happen is on OrderByDescending the nulls will be at the end, vs with this method the nulls will be at the beginning. Which is useful if you want to shuffle nulls around without splitting data into pieces and splicing it later.
LastOrDefault() is usually not working but with the Tolist() it will work. There is no need to use OrderByDescending use Tolist() like this.
GroupBy(p => p.Nws_ID).ToList().LastOrDefault();