I've got a table Installation which can contains one or many Equipements.
And for functionnal reasons, I've overwritten my table Installation and added a field NbrEquipements.
I want to fill this field with Linq, but I'm stuck...
Due to special reasons, there is no relation between these to tables. So, no Installation.Equipements member into my class. Therefore, no Installation.Equipements.Count...
I'm trying some stuff. Here is my code:
var query = RepoInstallation.AsQueryable();
// Some filter
query = query.Where(i => i.City.RegionId == pRegionId));
int?[] etatIds = { 2, 3 };
query = (from i in query
select new Installation
{
NbrEquipements= (from e in RepoEquipement.AsQueryable()
where e.InstallationSpecialId == i.SpecialId
&& (etatIds.Contains(e.EquEtat))
select e.SasId
).Count()
});
But with this try, I got this error:
The entity or complex type 'myModel.Installation' cannot be constructed in a LINQ to Entities query
I've tried some other stuff but I'm always turning around...
Another thing that can be useful for me: It would be great to fill a field called Equipements which is a List<Equipement>.
After that, I would be able to Count this list...
Is it possible ?
Tell me if I'm not clear.
Thanks in advance.
Here is the final code:
//In the class:
[Dependency]
public MyEntities MyEntities { get; set; }
//My Methode code:
var query = MyEntities .SasInstallations.AsQueryable();
// Some filter
query = query.Where(i => i.City.RegionId == pRegionId));
var liste = new List<Installation>();
var queryWithListEquipements =
from i in query
select new
{
Ins = i,
EquipementsTemp = (from eq in MyEntities.Equipements.AsQueryable()
where eq.SpecialId == i.SpecialId
&& (etatIds.Contains(eq.SasEquEtat))
select eq
).ToList()
};
var listWithListEquipements = queryWithListEquipements.ToList();
foreach (var anonymousItem in listWithListEquipements)
{
var ins = anonymousItem.Ins;
ins.Equipements = anonymousItem.EquipementsTemp;
ins.NumberEquipements = ins.Equipements.Count();
liste.Add(ins);
}
return liste;
By the way, this is very very fast (even the listing of Equipements). So this is working exactly has I wished. Thanks again for your help everyone!
Use an anonymous type. EF does not like to instantiate entity classes inside a query.
var results = (from i in query
select new
{
NbrEquipements= (from e in RepoEquipement
where e.InstallationSpecialId == i.SpecialId
&& (etatIds.Contains(e.EquEtat))
select e.SasId
).Count()
})
.ToList();
Notice how I used select new instead of select new Installation.
You can then use the data inside the list (which is now in memory) to create instances of type Installation if you want like this:
var installations = results.Select(x =>
new Installation
{
NbrEquipements = x.NbrEquipements
}).ToList();
Here is how to obtain the list of equipment for each installation entity:
var results = (from i in query
select new
{
Installation = i,
Equipment = (from e in RepoEquipement
where e.InstallationSpecialId == i.SpecialId
&& (etatIds.Contains(e.EquEtat))
select e).ToList()
})
.ToList();
This will return a list of anonymous objects. Each object will contain a property called Installation and another property called Equipment (which is a list). You can easily convert this list (of anonymous objects) to another list of whatever type that you want.
Related
I have a few tables and this is what I need to achieve.
This gets all the rows from one table
var FRA = from prod in _cctDBContext.Fra
where prod.ActTypeId == 1
From within that, I get all the rows where ActTypeID.
Then I need to query another table from with the ID's get from that
foreach (var item in FRA)
{
var FRSA = _cctDBContext.Frsa
.Select(p => new { p.Fraid, p.Frsa1,
p.Frsaid, p.CoreId,
p.RelToEstId, p.ScopingSrc,
p.Mandatory })
.Where(p => p.Fraid == item.Fraid)
.ToList();
}
I then need to push each one of these to Entity Framework. I usually do it this way:
foreach (var item in FRA)
{
var FinanicalReportingActivity = new FinancialReportingActivity { FinancialReportingActivityId = item.Fraid, ScopingSourceType = item.ScopingSrc, Name = item.Fra1, MandatoryIndicator = item.Mandatory, WorkEffortTypeId = 0 };
_clDBContext.FinancialReportingActivity.AddRange(FinanicalReportingActivity);
}
But because I have used 2 for each loops, I cannot get the variables to work because I cannot find a way to get local variables as the entity context.
Can anyone think of a better way to code this?
Thanks
It looks like you can do this as a single join:
var query =
from prod in _cctDBContext.Fra
where prod.ActTypeId == 1
join p in _cctDBContext.Frsa on prod.Fraid equals p.Fraid
select new
{
p.Fraid,
p.Frsa1,
p.Frsaid,
p.CoreId,
p.RelToEstId,
p.ScopingSrc,
p.Mandatory
};
It looks like you are loading data from one set of entities from one database and want to create matching similar entities in another database.
Navigation properties would help considerably here. Frsa appear to be a child collection under a Fra, so this could be (if not already) wired up as a collection within the Fra entity:
Then you only need to conduct a single query and have access to each Fra and it's associated Frsa details. In your case you look to be more interested in the associated FRSA details to populate this ReportingActivity:
var details = _cctDBContext.Fra
.Where(x => x.ActTypeId == 1)
.SelectMany(x => x.Frsa.Select(p => new
{
p.Fraid,
p.Frsa1,
p.Frsaid,
p.CoreId,
p.RelToEstId,
p.ScopingSrc,
p.Mandatory
}).ToList();
though if the relationship is bi-directional where a Fra contains Frsas, and a Frsa contains a reference back to the Fra, then this could be simplified to:
var details = _cctDBContext.Frsa
.Where(x => x.Fra.ActTypeId == 1)
.Select(p => new
{
p.Fraid,
p.Frsa1,
p.Frsaid,
p.CoreId,
p.RelToEstId,
p.ScopingSrc,
p.Mandatory
}).ToList();
Either of those should give you the details from the FRSA to populate your reporting entity.
I'm a little bit stuck, I took an new project but there is so timeout issue due to queries.
I don't know the syntax in linq to improve one querie even if i tried multiple times.
The query is :
var contactslist = (User as CustomPrincipal).contacts;
var contacts = from m in db.ADDR_DEST.toList()
from n in contactslist
where m.ADDR_COUNTRY == n.country && m.ADDR_TPL_TYPE == n.tpl_type
select m;
But I want to dosen't launch this query before that i had different parametre so i remove the .toList() for adding some condition with
contacts.where(..);
And then I would like launch my query but i got an error with the type which must be an list<> but in this case it's a Iqueryable.
Can you help me please?
Is there an other way to launch this query after I do all my settings?
You can do something like that:
db.ADDR_DEST.Join(contactslist,
addr => new { country = addr.ADDR_COUNTRY, type = addr.ADDR_TPL_TYPE },
cont => new { country = cont.country, type = cont.tpl_type },
(addr, cont) => addr)
.ToList();
Then, if you want to choose the contactlist that meet certain requirements:
db.ADDR_DEST.Join(contactslist.Where(...).ToList(),
addr => new { country = addr.ADDR_COUNTRY, type = addr.ADDR_TPL_TYPE },
cont => new { country = cont.country, type = cont.tpl_type },
(addr, cont) => addr)
.ToList();
I hope you find it useful
Try (not tested):
var contacts = db.ADDR_DEST.Where(m => m.COUNTRY == contactslist.country
&& m.ADDR_TPL_TYPE == contactslist.tpl_type)
.ToList();
If contactslist is a list then try the following
var contacts = (from addr in db.ADDR_DEST
join cl in contactslist on
new {addr.COUNTRY, addr.ADDR_TPL_TYPE} equals new {cl.country, cl.tpl_type}
select new {addr})
.ToList();
The Linq join is easier to understand than its lambda equivalent!
There are some good examples here
I have a table, lets say tblCar with all the related columns like Id, Make, Model, Color etc.
I have a search model for car containing two params Id and Model.
public class CarSearch
{
public int Id { get; set; }
public string Model { get; set; }
}
var carSearchObjets = new List<CarSearch>();
With list of primitive data (like Id list), to get cars with those Ids I could have done:
var idList = new List<int> { 1, 2, 3 };
var carsFromQuery = context.Cars.Where(x => idList.Contains(x.Id);
But if I have to fetch all the cars with Id and model from the list, how do I do it? Simple join cannot be done between in memory objects and tables.
I need something like,
from m in context.Cars
join n in carSearchObjets
on new { Id = n.Id, Model = n.Model } equals new { Id = m.Id, Model = m.Model }
select m;
This obviously won't work.
Please ignore any typos.And if you need more info or the question is not clear, let me know.
One (ugly-but-working) way to manage that is to use concatenation with a "never used" concat char.
I mean a char that should never appear in the datas. This is always dangerous, as... never is never sure, but you've got the idea.
For example, we'll say that our "never used" concat char will be ~
This is not good for perf, but at least working :
var carSearchObjectsConcatenated = carSearchObjets.Select(m => new { m.Id + "~" + m.Model});
then you can use Contains again (concatenating on the db too) : you'll need to use SqlFunctions.StringConvert if you wanna concatenate string and numbers on the db side.
var result = context.Cars.Where(m =>
carSearchObjectsConcatenated.Contains(SqlFunctions.StringConvert((double)m.Id) + "~" + m.Model);
EDIT
Another solution would be to use PredicateBuilder, as mentionned by Sorax, or to build your own Filter method if you don't want a third party lib (but PredicateBuilder is really fine).
Something like that in a static class :
public static IQueryable<Car> FilterCars(this IQueryable<Car> cars, IEnumerable<SearchCar> searchCars)
{
var parameter = Expression.Parameter(typeof (Car), "m");
var idExpression = Expression.Property(parameter, "Id");
var modelExpression = Expression.Property(parameter, "Model");
Expression body = null;
foreach (var search in searchCars)
{
var idConstant = Expression.Constant(search.Id);
var modelConstant = Expression.Constant(search.Model);
Expression innerExpression = Expression.AndAlso(Expression.Equal(idExpression, idConstant), Expression.Equal(modelExpression, modelConstant));
body = body == null
? innerExpression
: Expression.OrElse(body, innerExpression);
}
var lambda = Expression.Lambda<Func<Car, bool>>(body, new[] {parameter});
return cars.Where(lambda);
}
usage
var result = context.Cars.FilterCars(carSearchObjets);
this will generate an sql looking like
select ...
from Car
where
(Id = 1 And Model = "ax") or
(Id = 2 And Model = "az") or
(Id = 3 And Model = "ft")
'PredicateBuilder' might be helpful.
var predicate = PredicateBuilder.False<Car>();
carSearchObjects
.ForEach(a => predicate = predicate.Or(p => p.Id == a.Id && p.Model == a.Model));
var carsFromQuery = context.Cars.AsExpandable().Where(predicate);
Note the text in the link regarding EF:
If you're using Entity Framework, you'll need the complete LINQKit -
for the AsExpandable functionality. You can either reference
LINQKit.dll or copy LINQKit's source code into your application.
Old school solution..
//in case you have a
List<CarSearch> search_list; //already filled
List<Cars> cars_found = new List<Cars>();
foreach(CarSearch carSearch in search_list)
{
List<Cars> carsFromQuery = context.Cars.Where(x => x.Id == carSearch.Id && x.Model == carSearch.Model).ToList();
cars_found.AddRange(carsFromQuery);
}
Abd don't worry about the for loops.
I landed up passing in an xml list as a parameter to the sql query and joined to that:
var xml = new XElement("Cars", yourlist.Select(i => new XElement("Car", new XElement("Id", i.Id), new XElement("Model", i.Model))));
var results = Cars
.FromSql("SELECT cars.*"
+ "FROM #xml.nodes('/Cars/Car') Nodes(Node)"
+ "JOIN Cars cars on cars.Id = Nodes.Node.value('Id[1]', 'int') and cars.Model = Nodes.Node.value('Model[1]', 'varchar(100)')",
new SqlParameter("#xml", new SqlXml(xml.CreateReader())));
For entity-framework-core users I created a nuget package extension:
EntityFrameworkCore.SqlServer.Extensions.Contains
I have a page with five text boxes, each one representing a field in my database table and a search button:
If I were using SQL I could build my SQL statement depending on which fields have data in them.
However, I want to use LINQ, and I'm at a loss as to how to accomplish this. For instance, take a look at the query below:
var db = new BookDBDataContext();
var q =
from a in db.Books
where a.Title.Contains(txtBookTitle) &&
a.Author.Contains(txtAuthor) &&
a.Publisher.Contains(txtPublisher)
select a.ID;
The query above will return data where all the fields match data in the table. But, what if the user didn't enter an Author in the txtAuthor field? If I were building this as a query string, I could check each field for data and add it to the query string. Since this is LINQ, I can't dynamically change the search criteria, it seems.
Any advice would be greatly appreciated!
var db = new BookDBDataContext();
var q = (from a in db.Books
where a.Title.Contains(txtBookTitle));
if(!String.IsNullOrEmpty(txtAuthor))
{
q = q.Where(a => a.Author.Contains(txtAuthor));
}
if(!String.IsNullOrEmpty(txtAuthor))
{
q = q.Where(a => a.Publisher.Contains(txtPublisher));
}
var id = q.Select(a => a.ID);
from a in db.Books
where (string.isNullorWhiteSpace(search) || a.Title.Contains(search)) &&
(string.isNullorWhiteSpace(txtAuthor) || a.Author.Contains(txtAuthor) ) &&
(string.isNullorWhiteSpace(txtPublisher) || a.Publisher.Contains(txtPublisher))
select a.ID;
I need to retrieve a list of entities from my database that matches a list of items in a plain list (not EF). Is this possible with Entity Framework 4.1?
Example:
var list = new List<string> { "abc", "def", "ghi" };
var items = from i in context.Items
where list.Contains(i.Name)
select i;
This works great to return rows that match one property, but I actually have a more complex property:
var list = new List<Tuple<string, string>>
{
new Tuple<string,string>("abc", "123"),
new Tuple<string,string>("def", "456")
};
// i need to write a query something like this:
var items = from i in context.Items
where list.Contains(new Tuple<string,string>(i.Name, i.Type))
select i;
I know that is not valid because it will say it needs to be a primitive type, but is there any way to do what I'm trying to accomplish or will I need to resort to a stored procedure?
You have a few options:
1) You could, of course, write a stored procedure to do what you need and call it.
2) You could read the table into memory and then query the in memory list...that way you don't have to use primitives:
var items = from i in context.Items.ToList()
where list.Contains(new Tuple<string, string>(i.Name, i.Type))
select i;
3) You could also convert your query to use primitives to achieve the same goal:
var items = from i in context.Items
join l in list
on new { i.Name, i.Type } equals
new { Name = l.Item1, Type = l.Item2 }
select i;
I would go with the second option as long as the table isn't extremely large. Otherwise, go with the first.
You need to break it down to sub-properties. For example, something like (this might not compile, i'm not able to test at the moment, but it should give you something to work with):
var items = from i in context.Items
where list.Select(x => x.Item1).Contains(i.Name)
&& list.Select(x => x.Item2).Contains(i.Type)
select i;
You have to think about what the resulting SQL would look like, this would be difficult to do directly in SQL.
My suggestion would be you split out one field of the tuples and use this to cut down the results list, get back the query result then filter again to match one of the tuples e.g.
var list = new List<string> { "abc", "def" };
var list2 = new List<Tuple<string, string>>
{
new Tuple<string,string>("abc", "123"),
new Tuple<string,string>("def", "456")
};
var items = (from i in context.Items
where list.Contains(i.Name)
select i)
.AsEnumerable()
.Where(i => list2.Any(j => j.val1 == i.Name && j.val2 == i.Type);