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
{
}
}
In my Edit Controller Action, I post the object to update.
[HttpPost]
public virtual ActionResult Edit(Case myCase){
var currentDocuments = db.CaseDocuments.Where(p => p.idCase == myCase.idCase);
foreach (CaseDocument docInDB in currentDocuments )
{
var deleteDoc = true;
foreach (CaseDocument docNew in myCase.CaseDocuments )
{
if (docNew.idDocument == docInDB.idDocument)
deleteDoc = false;
}
if (deleteDoc )
db.CaseDocuments.Remove(docInDB);
}
foreach (CaseDocument pc in myCase.CaseDocuments)
{
if (pc.idDocument == 0)
db.CaseDocuments.Add(pc);
else
db.Entry(pc).State = EntityState.Modified;
}
*** **db.Entry(myCase).State = EntityState.Modified;** //THIS LINE
db.SaveChanges();
}
The Case model has a collection of Documents, and they are posted along with the Case Model.
As soon I enter the action, I can count the number of documents in the collection, and lets say there are 3.
Then, in order to see if I need to delete documents from database (as the user deleted one from UI), I need to get the Documents for that case from database in this way:
var currentDocuments = db.CaseDocuments.Where(p => p.idCase == myCase.idCase);
And here starts the weird thing: as soon I executa that statement, the myCase.Documents is loaded with what it is in database (lets say there are 4)!! So, I'm not able to compare the 2 collections (to detect if a document was deleted and remove it from db).
What I need is during the Edit Action of my Case model, I need to create/update/modify its documents. Do I need to see this from other angle? What I'm doing is wrong?
EDIT:
After the comments, I realized that the line where I marked myCase as Modified, was at the begining, and I suppose that this was the reason for that behaviour.
Now, moving that line to just before the db.SaveChanges(), fixed that problem, but at the db.Entry(myCase).State = EntityState.Modified; says "There is already an object with the same key in ObjectStateManager. "
What am I doing wrong here? This code looks bad!
Try it this way:
[HttpPost]
public virtual ActionResult Edit(Case myCase){
var currentDocumentIds = db.CaseDocuments
.Where(p => p.idCase == myCase.idCase)
.Select(p => p.idDocument);
foreach (int idInDb in currentDocumentsIds.Where(i => !myCase.CaseDocuments
.Any(ci => ci.idDocumnet == i))
{
var docToDelete = new CaseDocument { idDocument = idInDb };
db.CaseDocuments.Remove(docToDelete);
}
foreach (CaseDocument pc in myCase.CaseDocuments)
{
if (pc.idDocument == 0)
db.CaseDocuments.Add(pc);
else
db.Entry(pc).State = EntityState.Modified;
}
db.Entry(myCase).State = EntityState.Modified;
db.SaveChanges();
}
Edit: The difference between this code and your code is the way how it works with existing documents. It doesn't load them - it loads just their ids. This way you will save some data transfer from database but it should also help you avoiding that exception. When you load the document from the database you have it already attached in the context but if you try to call this:
db.Entry(pc).State = EntityState.Modified;
you will try to attach another instance of the document with the same key to the context. That is not allowed - context can have attached only single instance with unique key.
So I'm working through a simplified example of my hoped-for database that has the following tables:
Contractors: Id, ContractorName
Types: Id, TypeName
CoverageZips: ContractorId, Zip
TypesForContractors: ContractorId, TypeId
where contractors can have many zips and types and types and zips can have many contractors (many-to-many).
I'm trying to:
do a search for contractors in a certain zip code
then load the types for those contractors.
The SQL for the first part would probably look like:
SELECT * FROM dbo.Contractors WHERE Id IN
(SELECT ContractorId FROM dbo.CoverageZips WHERE Zip = 12345)
Here's what I have for the first part in Simple.Data. It's working, but I feel like I'm missing some of the beauty of Simple.Data...
List<int> contractorIds = new List<int>();
foreach(var coverage in _db.CoverageZips.FindAllByZip(zip)) {
contractorIds.Add((int)coverage.ContractorId);
}
var contractors = new List<dynamic>();
if (contractorIds.Count > 0) {
contractors = _db.Contractors.FindAllById(contractorIds).ToList<dynamic>();
}
return contractors;
That's working ok until I try part 2:
public dynamic GetAllForZip(int zip) {
List<int> contractorIds = new List<int>();
foreach(var coverage in _db.CoverageZips.FindAllByZip(zip)) {
contractorIds.Add((int)coverage.ContractorId);
}
var contractors = new List<dynamic>();
if (contractorIds.Count > 0) {
contractors = _db.Contractors.FindAllById(contractorIds).ToList<dynamic>();
}
foreach (var contractor in contractors) {
// Exception occurs here on second iteration
// even though the second contractor was originally in the contractors variable
contractor.types = GetTypesForContractor((int)contractor.Id);
}
return contractors;
}
public dynamic GetTypesForContractor(int id) {
var types = new List<dynamic>();
if (id > 0) {
List<int> typeIds = new List<int>();
foreach (var typeForContractor in _db.TypesForContractor.FindAllByContractorId(id)) {
typeIds.Add((int)typeForContractor.TypeId);
}
if (typeIds.Count > 0) {
types = _db.ContractorTypes.FindAllById(typeIds).ToList<dynamic>();
}
}
return types;
}
I set a breakpoint and everything works ok for the first iteration showing , but is failing on the second with the following exception:
Index was out of range. Must be non-negative and less than the size of the collection.
tl;dr
I'm not sure how to properly use many-to-many relationships with Simple.Data and something weird is happening when I try my method more than once
I don't know what's happening with that exception and will investigate today.
You are missing some beauty, though. Assuming you have referential integrity configured on your database (which of course you do ;)), your methods can be written thus:
public dynamic GetAllForZip(int zip) {
var contractors = _db.Contractors
.FindAll(_db.Contractors.ContractorZips.Zip == zip)
.ToList();
foreach (var contractor in contractors) {
contractor.Types = GetTypesForContractor((int)contractor.Id);
}
return contractors;
}
public dynamic GetTypesForContractor(int id) {
return _db.ContractorTypes
.FindAll(_db.ContractorTypes.TypesForContractor.ContractorId == id)
.ToList();
}
Update!
As of 1.0.0-beta3, eager-loading across many-to-many joins is supported, so now you can do this:
public dynamic GetAllForZip(int zip) {
return _db.Contractors
.FindAll(_db.Contractors.ContractorZips.Zip == zip)
.With(_db.Contractors.TypesForContractor.ContractorTypes.As("Types"))
.ToList();
}
And that executes as a single SQL select to make your DBA happy like rainbow kittens.
i am developing an application in mvc3.
I have two dropdowns and on the basis of value selected in first dropdown the second dropdown is populated.
The first dropdown is Course and on the basis of course selected the second dropdown populates the states where the course is available.
Foreg.if the course is 'MCA' the states should be Maharashtra,rajasthan and so-on.
For this i have written an ajax function which is working fine.
But the problem is i am not able to fetch multiple states at a time that is i can fetch only One state at a time.
I have written the following Code to fetch the state name:
HobbyHomeAdress Table contains ProvincialStateID which i fetch through some other method.
Then i compare that value with the value in ProvincialStateID in ProvincialState Table and fetch the data of that table but with it gives me the last record only.
public ICollection<ProvincialState> FetchStateByStateid(ICollection<HobbyHomeAddress> hobbyhomeaddresslist)
{
log.Debug("Start");
ISession session = DataAccessLayerHelper.OpenWriterSession();
ITransaction transaction = session.BeginTransaction();
ICollection<ProvincialState> provincialstate = null;
try
{
foreach (var state in hobbyhomeaddresslist)
{
provincialstate = session.CreateCriteria(typeof(ProvincialState))
.Add(Expression.Eq("ProvincialStateID", state.ProvincialState.ProvincialStateID))
.List<ProvincialState>();
}
transaction.Commit();
}
catch (SessionException ex)
{
if (transaction != null && transaction.IsActive)
transaction.Rollback();
log.Error(ex);
provincialstate = null;
}
finally
{
if (transaction != null)
transaction.Dispose();
if (session != null && session.IsConnected)
session.Close();
log.Debug("End");
}
return provincialstate;
}
you are recreating the provincialstate collection for each state in hobbyhomeaddresslist. So you end up with a collection with a single entry, usually the last one. Instead you should create the collection upfront and after retrieving an item, just add it to that collection.
...snip
...
List<ProvincialState> provincialstate = new List<ProvincialState>();
try
{
foreach (var state in hobbyhomeaddresslist)
{
var list = session.CreateCriteria(typeof(ProvincialState))
.Add(Expression.Eq("ProvincialStateID", state.ProvincialState.ProvincialStateID))
.List<ProvincialState>();
provincialstate.AddRange(list);
}
transaction.Commit();
}
...
Update: single query using a Disjunction.
IList<ProvincialState> provincialstate = null;
Disjunction dj = new Disjunction();
try
{
foreach (var state in hobbyhomeaddresslist)
{
dj.Add(Expression.Eq("ProvincialStateID", state.ProvincialState.ProvincialStateID));
}
provincialstate = session.CreateCriteria(typeof(ProvincialState))
.Add(dj)
.List<ProvincialState>();
transaction.Commit();
}
if you look at the generated SQL, you should now see a single select with several where clauses instead of several selects with a single where clause.
I have a couple of tables with similar relationship structure to the standard Order, OrderLine tables.
When creating a data context, it gives the Order class an OrderLines property that should be populated with OrderLine objects for that particular Order object.
Sure, by default it will delay load the stuff in the OrderLine property but that should be fairly transparent right?
Ok, here is the problem I have: I'm getting an empty list when I go MyOrder.OrderLines but when I go myDataContext.OrderLines.Where(line => line.OrderId == 1) I get the right list.
public void B()
{
var dbContext = new Adis.CA.Repository.Database.CaDataContext(
"<connectionString>");
dbContext.Connection.Open();
dbContext.Transaction = dbContext.Connection.BeginTransaction();
try
{
//!!!Edit: Imortant to note that the order with orderID=1 already exists
//!!!in the database
//just add some new order lines to make sure there are some
var NewOrderLines = new List<OrderLines>()
{
new OrderLine() { OrderID=1, LineID=300 },
new OrderLine() { OrderID=1, LineID=301 },
new OrderLine() { OrderID=1, LineID=302 },
new OrderLine() { OrderID=1, LineID=303 }
};
dbContext.OrderLines.InsertAllOnSubmit(NewOrderLines);
dbContext.SubmitChanges();
//this will give me the 4 rows I just inserted
var orderLinesDirect = dbContext.OrderLines
.Where(orderLine => orderLine.OrderID == 1);
var order = dbContext.Orders.Where(order => order.OrderID == 1);
//this will be an empty list
var orderLinesThroughOrder = order.OrderLines;
}
catch (System.Data.SqlClient.SqlException e)
{
dbContext.Transaction.Rollback();
throw;
}
finally
{
dbContext.Transaction.Rollback();
dbContext.Dispose();
dbContext = null;
}
}
So as far as I can see, I'm not doing anything particularly strange but I would think that orderLinesDirect and orderLinesThroughOrder would give me the same result set.
Can anyone tell me why it doesn't?
You're just adding OrderLines; not any actual Orders. So the Where on dbContext.Orders returns an empty list.
How you can still find the property OrderLines on order I don't understand, so I may be goofing up here.
[Edit]
Could you update the example to show actual types, especially of the order variable? Imo, it shoud be an IQueryable<Order>, but it's strange that you can .OrderLines into that. Try adding a First() or FirstOrDefault() after the Where.