So I'm new to linq so be warned what I'm doing may be completely stupid!
I've got a table of caseStudies and a table of Services with a many to many relasionship
the case studies already exist and I'm trying to insert a service whilst linking some case studies that already exist to it. I was presuming something like this would work?
Service service = new Service()
{
CreateDate = DateTime.Now,
CreatedBy = (from u in db.Users
where u.Id == userId
select u).Take(1).First(),
Description = description,
Title = title,
CaseStudies = (from c in db.CaseStudies
where c.Name == caseStudy
select c),
Icon = iconFile,
FeatureImageGroupId = imgGroupId,
UpdateDate = DateTime.Now,
UpdatedBy = (from u in db.Users
where u.Id == userId
select u).Take(1).First()
};
But This isn't correct as it complains about
Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Data.Objects.DataClasses.EntityCollection'
Can somebody please show me the correct way.
Thanks in advance
Yo have to add the query result to the case studies collection instead of trying to replace it.
var service = new Service { ... };
foreach (var caseStudy in db.CaseStudies.Where(s => s.Name == caseStudyName)
{
service.CaseStudies.Add(caseStudy);
}
You can wrap this in an extension method and get a nice syntax.
public static class ExtensionMethods
{
public static void AddRange<T>(this EntityCollection<T> entityCollection,
IEnumerable<T> entities)
{
// Add sanity checks here.
foreach (T entity in entities)
{
entityCollection.Add(entity);
}
}
}
And now you get the following.
var service = new Service { ... };
service.CaseStudies.AddRange(db.CaseStudies.Where(s => s.Name == caseStudyName));
Related
Appearently, I got an error if using the following code. It said:
Cannot implicity converrt type System.Linq.IQueryable<AnonymousType> to System.Collection.Generic.IEnumerable.
Please advise how I can fix this?
public IEnumerable<Session> GetAllListDetailConsumer(string refId)
{
ObjectQuery<Session> sessions = db.Sessions;
ObjectQuery<SessionsList> sessionsLists = db.SessionsList;
var query =
from s in sessions
join sList in sessionsLists on s.ReferralListID equals sList.ReferralListID
where s.ReferralListID == new Guid(refId)
select new SessionConsumerList
{
ReferralListID = s.ReferralListID,
SessionServerId = s.SessionServerID,
ApplicationID = s.ApplicationID,
// ...
ConsumerID = sList.ConsumerID,
ConsumerFirstName = sList.ConsumerFirstName,
ConsumerFamilyName = sList.ConsumerFamilyName,
// ...
};
return query.ToList();
}
You are selecting using select new, which would create an anonymous type, you need to project to class Session in your query like.
select new Session
{
....
But remember if your Session class is a representing a table in your database/data context, then you can't project to that class, instead you may have to create a temporary class and project the selection to that class.
EDIT (Since the question now has been edited)
Now you are selecting new SessionConsumerList and you are returning IEnumerable<Session>, you need to modify method signature to return IEnumerable<SessionConsumerList>
Why not separate the creation of the SessionConsumerList in another method? Makes the code a lot cleaner. Like this:
public static SessionConsumerList CreateSessionConsumerList(
Session s,
SessionsList sList)
{
return new SessionConsumerList
{
ReferralListID = s.ReferralListID,
SessionServerId = s.SessionServerID,
ApplicationID = s.ApplicationID,
// ...
ConsumerID = sList.ConsumerID,
ConsumerFirstName = sList.ConsumerFirstName,
ConsumerFamilyName = sList.ConsumerFamilyName,
// ...
};
}
And then:
var query =
from s in sessions
join sList in sessionsLists on s.ReferralListID equals sList.ReferralListID
where s.ReferralListID == new Guid(refId)
select CreateSessionConsumerList(s, sList);
Using Linq commands and Linq To SQL datacontext, Im trying to instance an Entity called "Produccion" from my datacontext in this way:
Demo.View.Data.PRODUCCION pocoProduccion =
(
from m in db.MEDICOXPROMOTORs
join a in db.ATENCIONs on m.cmp equals a.cmp
join e in db.EXAMENXATENCIONs on a.numeroatencion equals e.numeroatencion
join c in db.CITAs on e.numerocita equals c.numerocita
where e.codigo == codigoExamenxAtencion
select new Demo.View.Data.PRODUCCION
{
cmp = a.cmp,
bonificacion = comi,
valorventa = precioEstudio,
codigoestudio = lblCodigoEstudio.Content.ToString(),
codigopaciente = Convert.ToInt32(lblCodigoPaciente.Content.ToString()),
codigoproduccion = Convert.ToInt32(lblNroInforme.Content.ToString()),
codigopromotor = m.codigopromotor,
fecha = Convert.ToDateTime(DateTime.Today.ToShortDateString()),
numeroinforme = Convert.ToInt32(lblNroInforme.Content.ToString()),
revisado = false,
codigozona = (c.codigozona.Value == null ? Convert.ToInt32(c.codigozona) : 0),
codigoclinica = Convert.ToInt32(c.codigoclinica),
codigoclase = e.codigoclase,
}
).FirstOrDefault();
While executing the above code, I'm getting the following error that the stack trace is included:
System.NotSupportedException was caught
Message="The explicit construction of the entity type 'Demo.View.Data.PRODUCCION' in a query is not allowed."
Source="System.Data.Linq"
StackTrace:
en System.Data.Linq.SqlClient.QueryConverter.VisitMemberInit(MemberInitExpression init)
en System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
en System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
en System.Data.Linq.SqlClient.QueryConverter.VisitSelect(Expression sequence, LambdaExpression selector)
en System.Data.Linq.SqlClient.QueryConverter.VisitSequenceOperatorCall(MethodCallExpression mc)
en System.Data.Linq.SqlClient.QueryConverter.VisitMethodCall(MethodCallExpression mc)
en System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
en System.Data.Linq.SqlClient.QueryConverter.Visit(Expression node)
en System.Data.Linq.SqlClient.QueryConverter.VisitFirst(Expression sequence, LambdaExpression lambda, Boolean isFirst)
en System.Data.Linq.SqlClient.QueryConverter.VisitSequenceOperatorCall(MethodCallExpression mc)
en System.Data.Linq.SqlClient.QueryConverter.VisitMethodCall(MethodCallExpression mc)
en System.Data.Linq.SqlClient.QueryConverter.VisitInner(Expression node)
en System.Data.Linq.SqlClient.QueryConverter.ConvertOuter(Expression node)
en System.Data.Linq.SqlClient.SqlProvider.BuildQuery(Expression query, SqlNodeAnnotations annotations)
en System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
en System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression)
en System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source)
en Demo.View.InformeMedico.realizarProduccionInforme(Int32 codigoExamenxAtencion, Double precioEstudio, Int32 comi) en D:\cs_InformeMedico\app\InformeMedico.xaml.cs:línea 602
en Demo.View.InformeMedico.UpdateEstadoEstudio(Int32 codigo, Char state) en D:\cs_InformeMedico\app\InformeMedico.xaml.cs:línea 591
en Demo.View.InformeMedico.btnGuardar_Click(Object sender, RoutedEventArgs e) en D:\cs_InformeMedico\app\InformeMedico.xaml.cs:línea 683
InnerException:
Is that now allowed in LINQ2SQL?
Entities can be created outside of queries and inserted into the data store using a DataContext. You can then retrieve them using queries. However, you can't create entities as part of a query.
I am finding this limitation to be very annoying, and going against the common trend of not using SELECT * in queries.
Still with c# anonymous types there is a workaround, by fetching the objects into an anonymous type, and then copy it over into the correct type.
For example:
var q = from emp in employees where emp.ID !=0
select new {Name = emp.First + " " + emp.Last, EmployeeId = emp.ID }
var r = q.ToList();
List<User> users = new List<User>(r.Select(new User
{
Name = r.Name,
EmployeeId = r.EmployeeId
}));
And in the case when we deal with a single value (as in the situation described in the question) it is even easier, and we just need to copy directly the values:
var q = from emp in employees where emp.ID !=0
select new { Name = emp.First + " " + emp.Last, EmployeeId = emp.ID }
var r = q.FirstOrDefault();
User user = new User { Name = r.Name, EmployeeId = r.ID };
If the name of the properties match the database columns we can do it even simpler in the query, by doing select
var q = from emp in employees where emp.ID !=0
select new { emp.First, emp.Last, emp.ID }
One might go ahead and write a lambda expression that can copy automatically based on the property name, without needing to specify the values explictly.
Here's another workaround:
Make a class that derives from your LINQ to SQL class. I'm assuming that the L2S class that you want to return is Order:
internal class OrderView : Order { }
Now write the query this way:
var query = from o in db.Order
select new OrderView // instead of Order
{
OrderID = o.OrderID,
OrderDate = o.OrderDate,
// etc.
};
Cast the result back into Order, like this:
return query.Cast<Order>().ToList(); // or .FirstOrDefault()
(or use something more sensible, like BLToolkit / LINQ to DB)
Note: I haven't tested to see if tracking works or not; it works to retrieve data, which is what I needed.
I have found that if you do a .ToList() on the query before trying to contruct new objects it works
I just ran into the same issue.
I found a very easy solution.
var a = att as Attachment;
Func<Culture, AttachmentCulture> make =
c => new AttachmentCulture { Culture = c };
var culs = from c in dc.Cultures
let ac = c.AttachmentCultures.SingleOrDefault(
x => x.Attachment == a)
select ac == null ? make(c) : ac;
return culs;
I construct an anonymous type, use IEnumerable (which preserves deferred execution), and then re-consruct the datacontext object. Both Employee and Manager are datacontext objects:
var q = dc.Employees.Where(p => p.IsManager == 1)
.Select(p => new { Id = p.Id, Name = p.Name })
.AsEnumerable()
.Select(item => new Manager() { Id = item.Id, Name = item.Name });
Within the book "70-515 Web Applications Development with Microsoft .NET Framework 4 - Self paced training kit", page 638 has the following example to output results to a strongly typed object:
IEnumerable<User> users = from emp in employees where emp.ID !=0
select new User
{
Name = emp.First + " " + emp.Last,
EmployeeId = emp.ID
}
Mark Pecks advice appears to contradict this book - however, for me this example still displays the above error as well, leaving me somewhat confused. Is this linked to version differences? Any suggestions welcome.
I found another workaround for the problem that even lets you retain your result as IQueryale, so it doesn't actually execute the query until you want it to be executed (like it would with the ToList() method).
So linq doesn't allow you to create an entity as a part of query? You can shift that task to the database itself and create a function that will grab the data you want. After you import the function to your data context, you just need to set the result type to the one you want.
I found out about this when I had to write a piece of code that would produce a IQueryable<T> in which the items don't actually exist in the table containing T.
pbz posted a work around by creating a View class inherited from an entity class that you could be working with. I'm working with a dbml model of a table that has > 200 columns. When I try and return the whole table I get "Root Element missing" errors. I couldn't find anyone who wanted to deal with my particular issue so I was looking at rewriting my entire approach. Just creating a view class for the entitiy class worked in my case.
As pbz suggests : Create a view class that inherits from your entity class. For me this is tbCamp so :
internal class tbCampView : tbCamp
{
}
Then use the view class in your query :
using (var dc = ConnectionClass.Connect(Dev))
{
var camps = dc.tbCamps.Select(s => new tbCampView
{
active = s.active,
idCamp = s.idCamp,
campName = s.campName
});
SmartTableViewer(camps, dg1);
}
private void SmartTableViewer<T>(IEnumerable<T> allRecords)
{
// Build sorted rows back into new table
var table = new DataTable();
// Create columns based on type
if (allRecords is IEnumerable<tbCamp> tbCampRecords)
{
// Get the columns you want
table.Columns.Add("idCamp");
table.Columns.Add("campName");
foreach (var record in tbCampRecords)
{
// Make a new row
var r = table.NewRow();
// Add the contents to each column of the row
r["idCamp"] = record.idCamp;
r["campName"] = record.campName;
// Add the row to the table.
table.Rows.Add(r);
}
}
else
{
MessageBox.Show("Unhandled type. Add support for new data type in SmartTableViewer()");
return;
}
// Update table in grid
dg1.DataSource = table.DefaultView;
}
Here is what happens when you try and create an entity class object in the query.
I didn't want to have to use an anonymous type if I could help it because I wanted the type to be tbCamp. Since tbCampView is of type tbCamp the is operator works well. see Brian Hasden's answer Passing a generic List<> in C#
I'm surprised this is even an issue but with larger tables I run into this error so I thought I would just show it here :
When trying to read this table into memory I get the following error. There are < 2000 rows but the columns are > 200 for each. I don't know if that is an issue or not.
If I just want a few columns I need to create a custom class and handle that which isn't that big of a pain. With the approach pbz provided I don't have to worry about it.
Here is the entire project in case it helps someone.
public partial class Form1 : Form
{
private const bool Dev = true;
public Form1()
{
InitializeComponent();
}
private void btnGetAllCamps_Click(object sender, EventArgs e)
{
using (var dc = ConnectionClass.Connect(Dev))
{
IQueryable<tbCampView> camps = dc.tbCamps.Select(s => new tbCampView
{
// Project columns as needed.
active = s.active,
idCamp = s.idCamp,
campName = s.campName
});
// pass in as a
SmartTableViewer(camps);
}
}
private void SmartTableViewer<T>(IEnumerable<T> allRecords)
{
// Build sorted rows back into new table
var table = new DataTable();
// Create columns based on type
if (allRecords is IEnumerable<tbCamp> tbCampRecords)
{
// Get the columns you want
table.Columns.Add("idCamp");
table.Columns.Add("campName");
foreach (var record in tbCampRecords)
{
//var newRecord = record;
// Make a new row
var r = table.NewRow();
// Add the contents to each column of the row
r["idCamp"] = record.idCamp;
r["campName"] = record.campName;
// Add the row to the table.
table.Rows.Add(r);
}
}
else
{
MessageBox.Show("Unhandled type. Add support for new data type in SmartTableViewer()");
return;
}
// Update table in grid
dg1.DataSource = table.DefaultView;
}
internal class tbCampView : tbCamp
{
}
}
This has been ruining my life for a few days now, time to ask...
I am using Entity Framework 4.0 for my app.
A Location (such as a house or office) has one or more facilities (like a bathroom, bedroom, snooker table etc..)
I want to display a checkbox list on the location page, with a checkbox list of facilities, with the ones checked that the location currently has.
My View Model for the facilities goes like this...
public class FacilityViewItem
{
public int Id { get; set; }
public string Name { get; set; }
public bool Checked { get; set; }
}
So when im passing the Location View Model to the UI, i want to pass a List<T> of facilities where T is of type FacilityViewItem.
To get the facilities that the location already has is simple - i make a query using Location.Facilities which returns an EntityCollection where T is of type Facility. This is because Facilities is a navigation property....
var facs = from f in location.Facilities
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name,
Checked = true
};
So here is where my problem lies - i want the rest of the facilities, the ones that the Location does not have.
I have tried using Except() and Any() and Contains() but i get the same error.
Examples of queries that do not work...
var restOfFacilities = from f in ctx.Facilities
where !hasFacilities.Contains(f)
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name
};
var restOfFacilities = ctx.Facilities.Except(facilitiesThatLocationHas);
var notFacs = from e in ctx.Facilities
where !hasFacilities.Any(m => m.FacilityId == e.FacilityId)
select new FacilityViewItem()
{
Id = e.FacilityId,
Name = e.Name
};
And the error i get with every implementation...
System.NotSupportedException was unhandled
Message=Unable to create a constant value of type 'Chapter2ConsoleApp.Facility'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
What am i overlooking here?
ironically enough i solved it in a matter of hours after i posted the question on here, after days of suffering.
The error is basically saying 'i dont know how to calculate what items are not included by comparing strongly typed objects. Give me a list of Ints or some simple types, and i can take care of it'.
So, first you need to get a list of the primary keys, then use that in the contains clause...
//get the primary key ids...
var hasFacilityIds = from f in hasFacilities
select f.FacilityId;
//now use them in the contains clause...
var restOfFacilities = from f in ctx.Facilities
where !hasFacilityIds.Contains(f.FacilityId)
select new FacilityViewItem()
{
Id = f.FacilityId,
Name = f.Name
};
The first query seems fine, but you need to compare the Ids:
var restOfFacilities = from f in ctx.Facilities
where !facs.Select(fac => fac.Id).Contains(f.Id)
select f;
I wanna see what's hasFacilities, anyway, as L2E shows, "Only primitive types ('such as Int32, String, and Guid') are supported in this context", so I suppose you must retrieve first the data and put into a collection of FacilityViewItem.
var restOfFacilities = ctx
.Facilities
.Where(f => !hasFacilities.Contains(f))
.Select(f => new { f.FacilityId, f.Name })
.ToList()
.Select(f => new FacilityViewItem {
Id = f.FacilityId,
Name = f.Name
});
var notFacs = ctx
.Facilities
.Where(e => !hasFacilities.Any(m => m.FacilityId == e.FacilityId))
.Select(e => new { e.FacilityId, e.Name })
.ToList()
.Select(e => new FacilityViewItem {
Id = e.FacilityId,
Name = e.Name
});
hope it helps
OK I'm banging my head against a wall with this one ;-)
Given tables in my database called Address, Customer and CustomerType, I want to display combined summary information about the customer so I create a query to join these two tables and retrieve a specified result.
var customers = (from c in tblCustomer.All()
join address in tblAddress.All() on c.Address equals address.AddressId
join type in tblCustomerType.All() on c.CustomerType equals type.CustomerTypeId
select new CustomerSummaryView
{
CustomerName = c.CustomerName,
CustomerType = type.Description,
Postcode = address.Postcode
});
return View(customers);
CustomerSummaryView is a simple POCO
public class CustomerSummaryView
{
public string Postcode { get; set; }
public string CustomerType { get; set; }
public string CustomerName { get; set; }
}
Now for some reason, this doesn't work, I get an IEnumerable list of CustomerSummaryView results, each record has a customer name and a postcode but the customer type field is always null.
I've recreated this problem several times with different database tables, and projected classes.
Anyone any ideas?
I can't repro this issue - here's a test I just tried:
[Fact]
public void Joined_Projection_Should_Return_All_Values() {
var qry = (from c in _db.Customers
join order in _db.Orders on c.CustomerID equals order.CustomerID
join details in _db.OrderDetails on order.OrderID equals details.OrderID
join products in _db.Products on details.ProductID equals products.ProductID
select new CustomerSummaryView
{
CustomerID = c.CustomerID,
OrderID = order.OrderID,
ProductName = products.ProductName
});
Assert.True(qry.Count() > 0);
foreach (var view in qry) {
Assert.False(String.IsNullOrEmpty(view.ProductName));
Assert.True(view.OrderID > 0);
Assert.False(String.IsNullOrEmpty(view.CustomerID));
}
}
This passed perfectly. I'm wondering if you're using a reserved word in there?
This post seems to be referring to a similar issue...
http://groups.google.com/group/subsonicproject/browse_thread/thread/2b569539b7f67a34?hl=en&pli=1
Yes, the reason Rob's example works is because his projection's property names match exactly, whereas John's original example has a difference between CustomerType and type.Description.
This shouldn't have been a problem, but it was - the Projection Mapper was looking for properties of the same name and wasn't mapping a value if it didn't find a match. Therefore, your projection objects' properties would be default values for its type if there wasn't an exact name match.
The good news is, I got the latest source today and built a new Subsonic.Core.dll and the behavior is now fixed.
So John's code above should work as expected.
I just downloaded the latest build from 3/21/2010, which is about 2 months after the last poster on this thread, and the problem still exists in the packaged binary. Bummer.
Here what I have to do:
var data =
(from m in Metric.All()
where m.ParentMetricId == parentId
select new
{
m.MetricName,
m.MetricId,
})
.ToList();
var treeData =
from d in data
select new TreeViewItem
{
Text = d.MetricName,
Value = d.MetricId.ToString(),
LoadOnDemand = true,
Enabled = true,
};
return new JsonResult { Data = treeData };
If I try to do the projection directly from the Subsonic query, the Text property ends up with the ID, and the Value property ends up with the Name. Very strange.
My Techie Bretheren (and Sisteren, of course!),
I have a LinqToSql data model that has the following entities:
data model http://danimal.acsysinteractive.com/images/advisor.jpg
I need to retrieve all advisors for a specific office, ordered by their sequence within the office. I've got the first part working with a join:
public static List<Advisor>GetOfficeEmployees(int OfficeID)
{
List<Advisor> lstAdvisors = null;
using (AdvisorDataModelDataContext _context = new AdvisorDataModelDataContext())
{
var advisors = from adv in _context.Advisors
join advisoroffice in _context.OfficeAdvisors
on adv.AdvisorId equals advisoroffice.AdvisorId
where advisoroffice.OfficeId == OfficeID
select adv;
lstAdvisors = advisors.ToList();
}
return lstAdvisors;
}
However, I can't seem to wrap my weary brain around the order by clause. Can anyone give some suggestions?
from adv in _context.Advisors
where adv.OfficeAdvisor.Any(off => off.OfficeId == officeID)
order adv by adv.OfficeAdvisor.First(off => off.OfficeId = officeID).Sequence
select adv;
public static List<Advisor>GetOfficeEmployees(int OfficeID)
{
List<Advisor> lstAdvisors = null;
using (AdvisorDataModelDataContext _context = new AdvisorDataModelDataContext())
{
var advisors = from adv in _context.Advisors
join advisoroffice in _context.OfficeAdvisors
on adv.AdvisorId equals advisoroffice.AdvisorId
where advisoroffice.OfficeId == OfficeID
group adv by adv.OfficeId into g
order by g.Sequence
select g;
lstAdvisors = advisors.ToList();
}
return lstAdvisors;
}
Note: I am not able to currently test this on Visual Studio but should work.
You can add an order by clause like this:
var advisors = from adv in _context.Advisors
join advisoroffice in _context.OfficeAdvisors
on adv.AdvisorId equals advisoroffice.AdvisorId
where advisoroffice.OfficeId == OfficeID
orderby advisoroffice.Sequence // < -----
select adv;