I have the following DTO:
public int IdTableOne { get; set; }
public string ValueTableOne { get; set; }
public int IdTableTwo { get; set; }
public string ValueTableTwo { get; set; }
Also, I have two Models (TableOne & TableTwo) and I fill this models in my repository doing the following code:
return dbContext.TableOne;
At this point everything it's okay. TableOne & TableTwo are populated, but now I want to return the combination of these values into my DTO object (TableOneId is equal to TableTwoId, it's a relationship between both tables) for doing this I'm trying something like this:
public IEnumerable<TableOneAndTwoDTO> GetTableOneAndTwo()
{
List<TableOneAndTwoDTO> combination = new List<TableOneAndTwoDto>();
var t1 = myRepository.GetTableOne();
var t2 = myRepository.GetTableTwo();
var query = from p in t1
select new {
IdTableOne = p.Id,
ValueTableOne = p.Value,
};
foreach (var item in query)
{
combination.Add(new TableOneAndTwoDTO { IdTableOne = item.IdTableOne, ValueTableOne = item.ValueTableOne });
}
}
So my question is, how can I add the TableTwo values to my DTO only when IdTableOne = IdTableTwo.
You can join your table results. Something like this:
var query = from p in t1
join j in t2 on p.IdTableOne equals j.IdTableTwo
select new { p, j };
And then you can add the join values to your DTO using something like this:
foreach (var item in query)
{
combination.Add(new TableOnwAndTwoDTO { IdTableOne = item.p.IdTableOne, IdTableTwo = item.j.IdTableTwo... })
}
Just do a LINQ Join. You can avoid a lot of the ceremony from your original code by putting the whole thing into one query and then calling .ToList() before returning.
public IEnumerable<TableOneAndTwoDTO> GetTableOneAndTwo()
{
var t1 = myRepository.GetTableOne();
var t2 = myRepository.GetTableTwo();
var combination =
from p in t1
join j in t2 on p.IdTableOne equals j.IdTableTwo
select new {
IdTableOne = p.Id,
ValueTableOne = p.Value,
IdTableTwo = j.Id,
ValueTableTwo = j.Value,
};
return combination.ToList();
}
Related
Hi i convert sql query to linq i got this error. when i remove group by there isn't exception but i should use group by. why i got this exception ?
public List<BiontechSinovacCovidDto> GetBiontechSinovacCovidDto()
{
using(SirketDBContext context=new SirketDBContext())
{
var result =
from asi in context.Asilar
join covid in context.Covids
on asi.CovidId equals covid.CovidId
group asi by asi.AsiIsmi into isim
select new BiontechSinovacCovidDto
{
AsiIsmi=isim.Key,
//exception OrtalamaCovidSuresi=(EF.Functions.DateDiffDay(covid.CovidYakalanmaTarih, covid.CovidBitisTarih)).Average()
};
return result.ToList();
}
}
my sql query
Select
AsiIsmi,
AVG(Cast(DATEDIFF(Day,CovidYakalanmaTarih, CovidBitisTarih)AS FLOAT)) as OrtalamaCovidSuresi
From Asilar
INNER JOIN Covids on Covids.CovidId=Asilar.CovidId
group by AsiIsmi
|AsiIsmi| OrtalamaCovidSuresi|
------- ------------------
Biontech 13.6667
Sinovac 15
BiontechSinovacCovidDto
public class BiontechSinovacCovidDto
{
public string AsiIsmi { get; set; }
public double OrtalamaCovidSuresi { get; set; }
}
Average has overload which accepts lambda. You have to use this version. Also you have to group covid in this case.
public List<BiontechSinovacCovidDto> GetBiontechSinovacCovidDto()
{
using (var context = new SirketDBContext())
{
var result =
from asi in context.Asilar
join covid in context.Covids
on asi.CovidId equals covid.CovidId
group covid by asi.AsiIsmi into isim
select new BiontechSinovacCovidDto
{
AsiIsmi = isim.Key,
OrtalamaCovidSuresi = isim.Average(x => EF.Functions.DateDiffDay(x.CovidYakalanmaTarih, x.CovidBitisTarih))
};
return result.ToList();
}
}
I checked the questions that may already have my answer but it seems that none of them addresses the issue I have:
var semesters = db.Semesters.Where(e => e.ID == semester).ToList();
var semestersbyfaculty = db.SemestersByFaculty.Where(e => e.FacultyID == id).ToList();
How do I inner join these two queries like if I do the following in SQL:
SELECT
Fac.*, Sem.SemesterText
FROM
SemestersByFaculty AS Fac
INNER JOIN
Semesters AS Sem
ON
Fac.SemesterID = Sem.ID
WHERE id
Fac.FacultyID = id
Inner Join
The following example shows a simple inner equijoin.
var query = from fac in db.SemesterByFaculty
join sem in db.Semester on fac.SemesterID equals sem.ID
where fac.FacultyID == id
select new { Faculty = fac, SemesterText = sem.SemesterText };
For more information, see How to: Perform Inner Joins (C# Programming Guide).
UPDATE:
from comments
Models
class MyModel {
public MitModel.SemestersByFaculty Faculty{ get; set; }
public string SemesterText { get; set; }
}
class MyViewModel {
public List<MyModel> SemesterFaculties { get; set; }
}
Action:
public ActionResult SomeAction(string id) {
var query = from fac in db.SemesterByFaculty
join sem in db.Semester on fac.SemesterID equals sem.ID
where fac.FacultyID == id
select new MyModel{ Faculty = fac, SemesterTest = sem.SemesterTest };
var viewModel = new MyViewModel { SemesterFaculties = query.ToList() };
return View(viewModel);
}
View
#Model MyViewModel
Suppose you have following fields in SemestersByFaculty
class SemestersByFaculty
{
string FacultyName;
int FacultyID;
int SemesterID;
}
Note : If you have more fields in SemestersByFaculty class then you can list them in new{} in query below:
var query = semesters.Join(semestersbyfaculty,
sem => sem.ID,
fac => fac.SemesterID,
(sem, fac) =>
new { facName = fac.FacultyName, facId = fac.FacultyID,semText = sem.SemesterText }).Where(e=> e.fac.FacultyId = id);
Now , what you have got yourself is an enumerable. You can iterate over it and retrieve the values. It will be like:
foreach (var obj in query){
Console.writeln("{0}-{1}-{2}",obj.facName,obj.facId,obj.semText);
}
Here is solution with non-LINQ syntax. Also you can perform 'Where' filter on 'db.Semesters' and 'db.SemestersByFaculty' before they are passed into 'join'.
var result = db.SemestersByFaculty
.Where(
x_ => x_.FacultyID == id)
.Join(
db.Semesters.Where(x_ => x_.ID == semester),
x_ => x_.SemesterID,
x_ => x_.ID,
(x_, y_) => new
{
FacultyID = x_.ID,
SemesterID = y_.SemesterID,
Sem = y_.SemesterText
})
.ToList();
Is there a way to progressively / conditionally add joins to a query? I am creating a custom reporting tool for a client, and the client is given a list of objects he/she can select to query on. There will always be a base object used in the query ("FWOBid").
So, for example, if the customer selects objects "FWOBid", "FWOItem", and "FWOSellingOption", I'd want to do this:
var query = from fb in fwoBids
// if "FWOSellingOption", add this join
join so in sellingOptions on fb.Id equals so.BidId
// if "FWOItem", add this join
join i in fwoItems on fb.Id equals i.FWOBidSection.BidId
// select "FWOBid", "FWOItem", and "FWOSellingOption" (everything user has selected)
select new { FWOBid = fb, FWOSellingOption = so, FWOItem = i };
The trick is the customer can select about 6 objects that are all related to each other, resulting in many different combinations of joins. I'd like to avoid hard coding those if possible.
One option is to do some custom join combined with left joins.
A decent TSQL backend should not get any drawbacks in terms of performance for always using all the joins, since the optimers would just remove the join if the condition is always false. But this should be checked out.
bool joinA = true;
bool joinB = false;
bool joinC = true;
var query = from fb in fwoBids
join so in sellingOptions on new { fb.Id, Select = true } equals new { Id = so.BidId, Select = joinA } into js
from so in js.DefaultIfEmpty()
join i in fwoItems on new { fb.Id, Select = true } equals new { Id = i.FWOBidSection.BidId, Select = joinB } into ji
from i in ji.DefaultIfEmpty()
join c in itemsC on new { fb.Id, Select = true } equals new { Id = c.BidId, Select = joinC }
select new
{
FWOBid = fb,
FWOSellingOption = so,
FWOItem = i,
ItemC = c
};
In the Linq query syntax this is not possible, or looking at the other answers hardly readable. Not much more readable but another possibility would be to use the extension methods (sort of pseudo code):
bool condition1;
bool condition2;
List<Bid> bids = new List<Bid>();
List<SellingOption> sellingOptions = new List<SellingOption>();
List<Item> items = new List<Item>();
var result = bids.Select(x => new {bid = x, sellingOption = (SellingOption)null, item = (Item)null});
if (condition1)
result = result.Join(
sellingOptions,
x => x.bid.Id,
x => x.BidId,
(x, sellingOption) => new { x.bid, sellingOption, item = (Item)null });
if (condition2)
result = result.Join(
items,
x => x.bid.Id,
x => x.BidId,
(x, item) => new { x.bid, x.sellingOption, item });
Just see this as a sort of a concept. It is essentially the same that Peter Duniho did.
The thing is, if you don't want to immediately join on all options if not necessary, then it won't look that nice. Perhaps you should try to join all now and don't worry about performance. Have you ever measured how slow or fast it might be? Think of it as "I don't need it now!". If performance is indeed a problem, then you can act on it. But if it is not, and you won't know if you never tried, then leave it as the six joins you mentioned.
It's hard to provide a really good example solution without a really good example problem. However, what I mean by "chain the queries" is something like this:
var query = from x in dba select new { A = x, B = (B)null, C = (C)null };
if ((joinType & JoinType.B) != 0)
{
query = from x in query
join y in dbb on x.A.Id equals y.Id
select new { A = x.A, B = y, C = x.C };
}
if ((joinType & JoinType.C) != 0)
{
query = from x in query
join y in dbc on x.A.Id equals y.Id
select new { A = x.A, B = x.B, C = y };
}
That is, based on the appropriate condition, query the previous result with another join. Note that to do this successfully, each query must produce the same type. Otherwise, it's not possible to assign a new query to the previous query result variable.
Note that while in the above, I simply have a separate property for each possible input type, I could have instead had the type simply have properties for the input columns, Id, Name, and then the Text properties from the B and C types (which would have to be named differently in the query result type, e.g. TextB and TextC). That would look like this:
var query = from x in dba select new { Id = x.Id, Name = x.Name,
TextB = (string)null, TextC = (string)null };
if ((joinType & JoinType.B) != 0)
{
query = from x in query
join y in dbb on x.Id equals y.Id
select new { Id = x.Id, Name = x.Name, TextB = y.Text, TextC = x.TextC };
}
if ((joinType & JoinType.C) != 0)
{
query = from x in query
join y in dbc on x.Id equals y.Id
select new { Id = x.Id, Name = x.Name, TextB = x.TextB, TextC = y.Text };
}
Here is a complete code example that includes the above logic in a runnable program:
class A
{
public string Name { get; private set; }
public int Id { get; private set; }
public A(string name, int id)
{
Name = name;
Id = id;
}
public override string ToString()
{
return "{" + Name + ", " + Id + "}";
}
}
class B
{
public int Id { get; private set; }
public string Text { get; private set; }
public B(int id, string text)
{
Id = id;
Text = text;
}
public override string ToString()
{
return "{" + Id + ", " + Text + "}";
}
}
class C
{
public int Id { get; private set; }
public string Text { get; private set; }
public C(int id, string text)
{
Id = id;
Text = text;
}
public override string ToString()
{
return "{" + Id + ", " + Text + "}";
}
}
[Flags]
enum JoinType
{
None = 0,
B = 1,
C = 2,
BC = 3
}
class Program
{
static void Main(string[] args)
{
A[] dba =
{
new A("A1", 1),
new A("A2", 2),
new A("A3", 3)
};
B[] dbb =
{
new B(1, "B1"),
new B(2, "B2"),
new B(3, "B3")
};
C[] dbc =
{
new C(1, "C1"),
new C(2, "C2"),
new C(3, "C3")
};
JoinType joinType;
while ((joinType = _PromptJoinType()) != JoinType.None)
{
var query = from x in dba select new { A = x, B = (B)null, C = (C)null };
if ((joinType & JoinType.B) != 0)
{
query = from x in query
join y in dbb on x.A.Id equals y.Id
select new { A = x.A, B = y, C = x.C };
}
if ((joinType & JoinType.C) != 0)
{
query = from x in query
join y in dbc on x.A.Id equals y.Id
select new { A = x.A, B = x.B, C = y };
}
foreach (var item in query)
{
Console.WriteLine(item);
}
Console.WriteLine();
}
}
private static JoinType _PromptJoinType()
{
JoinType? joinType = null;
do
{
Console.Write("Join type ['A' for all, 'B', 'C', or 'N' for none]");
ConsoleKeyInfo key = Console.ReadKey();
Console.WriteLine();
switch (key.Key)
{
case ConsoleKey.A:
joinType = JoinType.BC;
break;
case ConsoleKey.B:
joinType = JoinType.B;
break;
case ConsoleKey.C:
joinType = JoinType.C;
break;
case ConsoleKey.N:
joinType = JoinType.None;
break;
default:
break;
}
} while (joinType == null);
return joinType.Value;
}
}
I hope this is an improvement over previous answers.
public class Bids
{
public int Id { get; set; }
public double Price { get; set; }
}
public class BidSection
{
public int BidId { get; set; }
}
public class SellingOptions
{
public int BidId { get; set; }
public int Quantity { get; set; }
}
public class Item
{
public int ItemId { get; set; }
public BidSection FWOBidSection { get; set; }
}
public class ConditionalJoin
{
public bool jOpt1 { get; set; }
public bool jOpt2 { get; set; }
public ConditionalJoin(bool _joinOption1, bool _joinOption2)
{
jOpt1 = _joinOption1;
jOpt2 = _joinOption2;
}
public class FBandSo
{
public Bids FWOBids { get; set; }
public SellingOptions FWOSellingOptions { get; set; }
}
public class FBandI
{
public Bids FWOBids { get; set; }
public Item FWOItem { get; set; }
}
public void Run()
{
var fwoBids = new List<Bids>();
var sellingOptions = new List<SellingOptions>();
var fwoItems = new List<Item>();
fwoBids.Add(new Bids() { Id = 1, Price = 1.5 });
sellingOptions.Add(new SellingOptions() { BidId = 1, Quantity = 2 });
fwoItems.Add(new Item() { ItemId = 10, FWOBidSection = new BidSection() { BidId = 1 } });
IQueryable<Bids> fb = fwoBids.AsQueryable();
IQueryable<SellingOptions> so = sellingOptions.AsQueryable();
IQueryable<Item> i = fwoItems.AsQueryable();
IQueryable<FBandSo> FBandSo = null;
IQueryable<FBandI> FBandI = null;
if (jOpt1)
{
FBandSo = from f in fb
join s in so on f.Id equals s.BidId
select new FBandSo()
{
FWOBids = f,
FWOSellingOptions = s
};
}
if (jOpt2)
{
FBandI = from f in fb
join y in i on f.Id equals y.FWOBidSection.BidId
select new FBandI()
{
FWOBids = f,
FWOItem = y
};
}
if (jOpt1 && jOpt2)
{
var query = from j1 in FBandSo
join j2 in FBandI
on j1.FWOBids.Id equals j2.FWOItem.FWOBidSection.BidId
select new
{
FWOBids = j1.FWOBids,
FWOSellingOptions = j1.FWOSellingOptions,
FWOItems = j2.FWOItem
};
}
}
}
I keep getting the error below on my code, and can't understand why it is having problems translating it to a query, it is pretty simple.
I have 2 repositories, Album and AlbumImage, when I fetch an album do I want a cover, that is a subselect in AlbumImages. What am I doing wrong here?
LINQ to Entities does not recognize the method
'System.Linq.IQueryable`1[Sogaard.us.Cosplay.Data.AlbumImage] Get()'
method, and this method cannot be translated into a store expression.
Album repository
public class AlbumRepository : IRepository<Album>
{
private CosplayEntities _entities;
private IRepository<AlbumImage> _imageRepository;
public AlbumRepository(CosplayEntities entities, IRepository<AlbumImage> imageRepository)
{
_entities = entities;
_imageRepository = imageRepository;
}
public IQueryable<Album> Get()
{
return (from a in _entities.Albums
select new Album()
{
Id = a.Id,
UserId = a.UserId,
Name = a.Name,
Created = a.Created,
LastEdit = a.LastEdit,
Description = a.Description,
Views = a.Views,
Location = a.Location,
Photoshoot = a.Photoshoot,
Cover = (from ai in _imageRepository.Get() where ai.AlbumId == a.Id orderby ai.Cover descending, ai.Id ascending select ai).FirstOrDefault(),
});
}
}
AlbumImage repository
public class AlbumImageRepository : IRepository<AlbumImage>
{
private CosplayEntities _entities;
public AlbumImageRepository(CosplayEntities entities)
{
_entities = entities;
}
public IQueryable<AlbumImage> Get()
{
return (from ai in _entities.AlbumImages
select new AlbumImage()
{
Id = ai.Id,
AlbumId = ai.AlbumId,
UserId = ai.UserId,
Type = ai.Type,
Width = ai.Width,
Height = ai.Height,
Description = ai.Description,
Views = ai.Views,
Uploadet = ai.Uploadet,
LastView = ai.LastView,
Thumblink = ai.Thumblink,
Imagelink = ai.Imagelink,
Cover = ai.Cover
});
}
This is the code i am getting the error on
_albumImageRepository = new AlbumImageRepository(_entities);
_albumRepository = new AlbumRepository(_entities, _albumImageRepository);
_albumImagesTagRepository = new AlbumImagesTagRepository(_entities);
....
var album = _albumRepository.Get().Where(x => x.Id == image.AlbumId).FirstOrDefault();
Update: I have commented the Cover = ... out in my IQueryable Get() so it is 2 simple select as object.
And i still get the error in something as simple as
model.Albums = (from a in _albumRepository.Get()
orderby a.Id descending
select new AlbumDisplayModel()
{
Album = a,
ImageCount = _albumImageRepository.Get().Where(x => x.AlbumId == a.Id).Count(),
User = _userRepository.Get().Where(x => x.Id == a.UserId).FirstOrDefault()
})
.Skip(AlbumsPrPage * (page - 1))
.Take(AlbumsPrPage).ToList();
Update 2: If i rewrite the IQueryable Get() to the following, do it work flawlessly, there there should really be no diffrence in how it is handled?
public IQueryable<Album> Get()
{
return (from a in _entities.Albums
select new Album()
{
Id = a.Id,
UserId = a.UserId,
Name = a.Name,
Created = a.Created,
LastEdit = a.LastEdit,
Description = a.Description,
Views = a.Views,
Location = a.Location,
Photoshoot = a.Photoshoot,
Cover = (from ai in _entities.AlbumImages where ai.AlbumId == a.Id orderby ai.Cover descending, ai.Id ascending select new AlbumImage()
{
Id = ai.Id,
AlbumId = ai.AlbumId,
UserId = ai.UserId,
Type = ai.Type,
Width = ai.Width,
Height = ai.Height,
Description = ai.Description,
Views = ai.Views,
Uploadet = ai.Uploadet,
LastView = ai.LastView,
Thumblink = ai.Thumblink,
Imagelink = ai.Imagelink,
Cover = ai.Cover
}).FirstOrDefault(),
});
}
Update 3: Did a little test, and the problem seems to be with Entity framework, se the following code, The var linqAlbum = testClass.LinqAlbumGet().ToList(); executes without any problems and return the correct data, var eeAlbum = testClass.EEAlbumGet().ToList(); fails with the exception
LINQ to Entities does not recognize the method
'System.Linq.IQueryable`1[RepositoryTest.TestAlbumCover] EEImageGet()'
method, and this method cannot be translated into a store expression.
My test script
class Program
{
static void Main(string[] args)
{
var linq = new LinqDataContext();
var ee = new NewCosplayEntities();
var testClass = new Test(linq, ee);
var linqAlbum = testClass.LinqAlbumGet().ToList();
var eeAlbum = testClass.EEAlbumGet().ToList();
}
}
public class Test
{
public NewCosplayEntities ee { get; set; }
public LinqDataContext linq { get; set; }
public Test(LinqDataContext linq, NewCosplayEntities ee)
{
this.linq = linq;
this.ee = ee;
}
public IQueryable<TestAlbum> LinqAlbumGet()
{
return from a in linq.Albums
select new TestAlbum
{
Id = a.Id,
Name = a.Name,
Cover = (from i in LinqImageGet() where i.AlbumId == a.Id select i).FirstOrDefault()
};
}
public IQueryable<TestAlbumCover> LinqImageGet()
{
return from i in linq.AlbumImages
select new TestAlbumCover()
{
Id = i.Id,
AlbumId = i.AlbumId
};
}
public IQueryable<TestAlbum> EEAlbumGet()
{
return from a in ee.Albums
select new TestAlbum
{
Id = a.Id,
Name = a.Name,
Cover = (from i in EEImageGet() where i.AlbumId == a.Id select i).FirstOrDefault()
};
}
public IQueryable<TestAlbumCover> EEImageGet()
{
return from i in ee.AlbumImages
select new TestAlbumCover()
{
Id = i.Id,
AlbumId = i.AlbumId
};
}
}
public class TestAlbum
{
public int Id { get; set; }
public string Name { get; set; }
public TestAlbumCover Cover { get; set; }
}
public class TestAlbumCover
{
public int Id { get; set; }
public int AlbumId { get; set; }
}
Your problem comes in the ItemRepository for Albumn. Specifically because _entities has no knowledge of the _imageRepository type, so it doesn't know how to translate that type into the appropriate TSQL script. You could cast the _entities.Albums.ToList() to force the IQueryable into an IEnumerable before you try to access the _ImageRepository.Get() from the scope of the hydrated object instead of directly on the database instance. Realize that you are then going to see a perf hit on the n+1 database requests for the AlbumImage child objects for each Album.
public IQueryable<Album> Get()
{
return (from a in _entities.Albums
select new Album()
{
Id = a.Id,
UserId = a.UserId,
Name = a.Name,
Created = a.Created,
LastEdit = a.LastEdit,
Description = a.Description,
Views = a.Views,
Location = a.Location,
Photoshoot = a.Photoshoot,
Cover = (from ai in _imageRepository.Get() where ai.AlbumId == a.Id orderby ai.Cover descending, ai.Id ascending select ai).FirstOrDefault(),
});
}
Ultimately, the problem is that your trying to use an ActiveRecord pattern rather than a true repository. Everything in a single IQueryable needs to be fetched through the same database context instance for parsing and tracking purposes.
Potentially its because you are wrapping the Album and AlbumImage in new references. I would remove that and do the projection after your query.
I don't think you can project into an entity and have each projection use a result from another IQueryable. If you replaced the contents of IQueryable<AlbumImage> Get() with this, it might work:
from a in _entities.Albums
join c in _imageRepository.Get() on a.Id equals c.AlbumId into acJoin
from ac in acJoin.DefaultIfEmpty()
select new Album()
{
Id = a.Id,
etc..,
etc..,
Cover = ac
}
I'm actually fairly certain that you will need to adjust this freehand query, but essentially it's joining the IQueryables, then projecting those results into your objects, instead of projecting to your objects then inserting an IQueryable into those results. Not the best explanation I know, but just look up "LINQ Left Join" or "Linq Left Outer Join" to see the syntax of what I'm describing here. Example
class Program
{
static void Main(string[] args)
{
MyDatabaseEntities entities = new MyDatabaseEntities();
var result = from c in entities.Categories
join p in entities.Products on c.ID equals p.IDCategory
group p by c.Name into g
select new
{
Name = g.Key,
Count = g.Count()
};
Console.WriteLine(result.ToString());
Console.ReadLine();
}
}
How can I extract the values from ths result set so I can work with them?
foreach (var item in result)
{
var name = item.Name;
var count = item.Count;
...
}
This will only work inside the same method where the LINQ query is located, since the compiler will only then know which properties are available in the anonymous object type (new { }) used in your LINQ select.
If you return a LINQ query to a calling method, and you want to access it in the way shown above, you'd have to define an explicit type and use it in your LINQ query:
class NameCountType
{
public string Name { get; set; }
public int Count { get; set; }
}
...
return from ... in ...
...
select new NameCountType
{
Name = ...,
Count = ...,
};
For example:
foreach (var x in result)
{
Console.WriteLine(x.c.Name);
}
var results = (from myRow in ds.Tables[0].AsEnumerable()
where myRow.Field<String>("UserName") == "XXX"
select myRow).Distinct();
foreach (DataRow dr in results)
UserList += " , "+dr[0].ToString();