I have an Alert class, with for example 10 properties. Two of the properties are [NotMapped] -
Then in my controller, I'm using Linq to join two tables to get the Alert class and a Customer class.
From the Customer class, there are two properties (customerName and customerAdmin) that I want to assign to the Alert class.
At the moment I'm doing this.....
var Alerts = (from a in alertrepository.Alerts
join code..........
Alerts = a
Customer = b
.................
select new Alert {
alertID = a.alertID,
applicantName = a.applicantName,
applicantEmail = a.applicantEmail,
applicantTelephone = a.applicantTelephone,
location = a.location,
dateSubmitted = a.dateSubmitted,
This - alertCustomerName= b.customerName,
This - alertCustomerAdmin= b.customerAdmin,
}).ToList();
Instead of having to declare a new Alert class again, and manually fill every property again as I am doing, is there any quicker way just to add individual properties?
For example, select a { a.alertCustomerName = b.customerName etc}
Related
I am trying to copy the grid data to one object.
Code :
object obj = GrdReport.ItemsSource;
PrepareDataForStackedChart1(obj);
The function is defined as
private void PrepareDataForStackedChart1(object categoies)
{
var Salespersons = (from cat in categoies
select cat.Salesperson);
}
I am getting error :
Cannot convert from 'lambda expression' to 'System.Linq.Expressions.LambdaExpression'
Can anyone tell me how I can access the object in a linq query?
Edit: Just happened to learn you are using a third party control (from your duplicate question) whose ItemSource property takes System.Object and not IEnumerable. In that case either cast your object (ItemSource) back to the original type, or maintain the original collection you used to bind the control somewhere and pass that collection to your PrepareDataForStackedChart1 method.
Some guess work:
1) Either
object obj = GrdReport.ItemsSource;
PrepareDataForStackedChart1((IEnumerable<Category>)obj);
private void PrepareDataForStackedChart1(IEnumerable<Category> categories)
{
var Salespersons = (from cat in categories
select cat.Salesperson);
}
2) or when you do
GrdReport.ItemsSource = GetCategories();
Copy a back up as well like this:
categories = GetCategories(); //categories is defined in proper scope.
GrdReport.ItemsSource = categories;
And later you do;
PrepareDataForStackedChart1(categories);
private void PrepareDataForStackedChart1(IEnumerable<Category> categories)
{
var Salespersons = (from cat in categories
select cat.Salesperson);
}
3) or may be you will get the collection from Items or Rows property (perhaps) defined on your GridView. Good luck..
Pre edit:
The error is because you cant enumerate a plain object. It has to be enumerable. Why are you passing an object value to your PrepareDataForStackedChart1 method? Instead can't you pass the IEnumerable itself? Try
var categories = GrdReport.ItemsSource.OfType<Category>();
PrepareDataForStackedChart1(categories);
private void PrepareDataForStackedChart1(IEnumerable<Category> categories)
{
var Salespersons = (from cat in categories
select cat.Salesperson);
}
I am assuming you have parent class Category
I have this bit of code that does not work because Entity Framework doesn't recognize the CreateItemDC method. CreateItemDC is a modular private method that creates a data contract for the given Item entity. I use CreateItemDC all throughout my service whenever I need to return an Item data contract, but I can't use it here. I can realize the sequence of ProjectItems into an array or enumerable because I would have to do this to all ProjectItem entities in my database as the query criteria is specified on the client and I don't have access to it here. Do I have any better options here? It seems that RIA Services is not worth the trouble. I'm really wishing I had used plain WCF with this project.
[Query]
public IQueryable<ProjectItemDC> GetProjectItems()
{
return from projectItem in ObjectContext.ProjectItems
select new ProjectItemDC
{
ID = projectItem.ID,
LibraryItem = CreateItemDC(projectItem.LibraryItem),
LibraryItemID = projectItem.LibraryItemID,
ProjectID = projectItem.ProjectID,
Quantity = projectItem.Quantity,
Width = projectItem.Width,
Height = projectItem.Height,
Depth = projectItem.Depth,
SheetMaterialID = projectItem.SheetMaterialID,
BandingMaterialID = projectItem.BandingMaterialID,
MaterialVolume = projectItem.MaterialVolume,
MaterialWeight = projectItem.MaterialWeight
};
}
P.S. I do love LINQ and E.F. though. :)
Well, if you want to go with plain WCF, you can, no problem, just change the code to
[Query(IsComposable=false)]
public IEnumerable<ProjectItemDC> GetProjectItems(string myParm1, string myParm2)
{
return from projectItem in ObjectContext.ProjectItems
select new ProjectItemDC
{
ID = projectItem.ID,
LibraryItem = CreateItemDC(projectItem.LibraryItem),
LibraryItemID = projectItem.LibraryItemID,
ProjectID = projectItem.ProjectID,
Quantity = projectItem.Quantity,
Width = projectItem.Width,
Height = projectItem.Height,
Depth = projectItem.Depth,
SheetMaterialID = projectItem.SheetMaterialID,
BandingMaterialID = projectItem.BandingMaterialID,
MaterialVolume = projectItem.MaterialVolume,
MaterialWeight = projectItem.MaterialWeight
}.ToArray();
}
write your own filtering/sorting logic and you're done.
Yes, you've lost WCF Ria Services dynamic query capabilities, but this is pretty much what you get with plain old WCF, isnt'it ?
If you instead need WCF Ria dynamic sorting/filtering/grouping you must take some additional steps, involving the visit of the Expression that WCF Ria Services create for you.
HTH
You can call ToArray() against ObjectContext.ProjectItems to force EF to load all the items, however, your query will no longer be composable on the client.
[Query]
public IQueryable<ProjectItemDC> GetProjectItems()
{
return from projectItem in ObjectContext.ProjectItems.ToArray()
select new ProjectItemDC
{
ID = projectItem.ID,
LibraryItem = CreateItemDC(projectItem.LibraryItem),
LibraryItemID = projectItem.LibraryItemID,
ProjectID = projectItem.ProjectID,
Quantity = projectItem.Quantity,
Width = projectItem.Width,
Height = projectItem.Height,
Depth = projectItem.Depth,
SheetMaterialID = projectItem.SheetMaterialID,
BandingMaterialID = projectItem.BandingMaterialID,
MaterialVolume = projectItem.MaterialVolume,
MaterialWeight = projectItem.MaterialWeight
};
}
Edit:
As mentioned in your comment, it gets all of the data out of the database at once which is not ideal. In order to create the LibraryItem with your private method, you cannot compose the query on the client. Instead, you should filter within the query method and then create the array.
[Query]
public IQueryable<ProjectItemDC> GetProjectItems(int id, string filter, object blah)
{
var projectItems = ObjectContext.ProjectItems.Where(...).ToArray();
return projectItems.Select(projectItem => new ProjectItemDC{...};
}
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
{
}
}
I just started using MS entity framework and have the following problem with LINQ. I will simplify my problem to make it clearer; let's say that I have three tables in SQL Server database:
CustomerData (PK is CustomerId, the table also has some twenty columns to hold customer data).
CustomerData1 (holds some data for the customer in one to one relationship).
CustomerData2 (also holds some data for the customer in one to one relationship).
I know the data with one to one relationship should better be in the same table, but this is some corporate db and it is not possible to alter the original table (so all our data should be in the separate tables).
Now I want to display a list of customer with their data from CustomerData table and add some data columns from CustomerData1 via join.
On the other hand, I want to display a list of customers and add some data from the other table CustomerData2 via join.
So the data is basically the same both times except that in the first case the result includes some columns from CustomerData1 and in the second case some data from CustomerData2 table.
So I created the class Customer with properties for all relevant columns in CustomerData table and added properties for columns that should be included from CustomerData1 and properties that should be included from CustomerData2.
All columns should be included each time, except that when first call will be made the properties that map to CustomerData2 table will be empty and during the second call the properties that map to CustomerData1 table will be empty.
For this I wanted to create one function so I tried to create it like this:
Input parameter in function is whether data from CustomerData1 or CustomerData2 is included.
if (firstList)
{
var query1 = from obj in CustomerData
join rel in CustomerData1
on obj.CustomerId equals rel.CustomerId
select new { obj, rel };
}
if (secondList)
{
var query2 = from obj in CustomerData
join rel in CustomerData2
on obj.CustomerId equals rel.CustomerId
select new { obj, rel };
}
So this code gives me the anonymous type based on the input parameter. Now I want to create Customer objects and order it (order is always the same, it does not depend on input parameter). So I want to create a list of ordered customers and include additional data based on the input parameter.
var query3 = <previous_query_variable>.Select(f => new Customer {
Id = f.obj.CustomerId,
Name = f.obj.CustomerName,
... other columns from Customer table (a lot of them)
//and then add some additional columns based on the input parameter
Data1 = f.rel.someDataFromCustomer1, //only when firstList == true, otherwise empty
Data2 = f.rel.someDataFromCustomer2 //only when secondList == true, otherwise empty
}).OrderBy(f => f.Name); //order by customer name
Of course this does not compile, since both vars are inside if statements. I know I could copy this last statement (var query3 = ...) inside both if statements and include only relevant assignments (Data1 or Data2), but I don't want to assign properties that map to CustomerData table twice (once in both if statements) nor I want to order twice.
How can I solve this problem? I am using .NET 4.
You cannot declare a variable for an anonymous type up-front, i.e. before your two if statements. (Something like var query = null is not supported.) You will have to create a helper type and project into it, like so:
public class ProjectedCustomerData
{
public CustomerData CustomerData { get; set; }
public CustomerData1 CustomerData1 { get; set; }
public CustomerData2 CustomerData2 { get; set; }
}
And then the projection:
IQueryable<ProjectedCustomerData> resultQuery = null;
if (firstList)
{
resultQuery = from obj in CustomerData
join rel in CustomerData1
on obj.CustomerId equals rel.CustomerId
select new ProjectedCustomerData
{
CustomerData = obj,
CustomerData1 = rel
};
}
if (secondList)
{
resultQuery = from obj in CustomerData
join rel in CustomerData2
on obj.CustomerId equals rel.CustomerId
select new ProjectedCustomerData
{
CustomerData = obj,
CustomerData2 = rel
};
}
var query3 = resultQuery.Select(f => new Customer {
Id = f.CustomerData.CustomerId,
Name = f.CustomerData.CustomerName,
// ...
Data1 = f.CustomerData1.someDataFromCustomer1,
Data2 = f.CustomerData2.someDataFromCustomer2
}).OrderBy(f => f.Name);
I am not sure if Customer is an entity in your model or only a class you are using for your projection. If it's an entity you have to change the last code because you cannot project into an entity (basically you would need another helper type for your projection).
how come this work
public IQueryable<Category> getCategories(int postId)
{
subnusMVCRepository<Categories> categories = new subnusMVCRepository<Categories>();
subnusMVCRepository<Post_Category_Map> postCategoryMap = new subnusMVCRepository<Post_Category_Map>();
var query = from c in categories.GetAll()
join pcm in postCategoryMap.GetAll() on c.CategoryId equals pcm.CategoryId
where pcm.PostId == 1
select new Category
{
Name = c.Name,
CategoryId = c.CategoryId
};
return query;
}
but this does not
public IQueryable<Category> getCategories(int postId)
{
subnusMVCRepository<Categories> categories = new subnusMVCRepository<Categories>();
subnusMVCRepository<Post_Category_Map> postCategoryMap = new subnusMVCRepository<Post_Category_Map>();
var query = from c in categories.GetAll()
join pcm in postCategoryMap.GetAll() on c.CategoryId equals pcm.CategoryId
where pcm.PostId == postId
select new Category
{
Name = c.Name,
CategoryId = c.CategoryId
};
return query;
}
The issue is most likely in the implementation of the query provider.
pcm.PostId == 1
and
pcm.PostId == postId
actually have a big difference. In the expression tree the first is generated as a ConstantExpression which doesnt need to be evaulated.
With the second, the compiler actually generates an inner class here (this is the _DisplayClassX that you see). This class will have a property (will most likely be the same name as your parameter) and the expression tree will create a MemberAccessExpression which points to the auto-generated DisplayClassX. When you query provider comes accross this you need to Compile() the Lambda expression and evaluate the delegate to get the value to use in your query.
Hope this helps.
cosullivan
The problem is not the linq itself,
you need to be sure that the context or provider object is able to fetch the data.
try testing the
subnusMVCRepository<Categories> categories = new subnusMVCRepository<Categories>();
subnusMVCRepository<Post_Category_Map> postCategoryMap = new subnusMVCRepository<Post_Category_Map>();
objects and see if they are populated or if they behaving as required.
you may want to search the generated code for c__DisplayClass1 and see what you can see there. some times the generated code dose some weird things.
when you step into you code check the locals and the variable values. this may also give you some clues.
Edit : Have you tried to return a List<> collection ? or an Enumerable type?
Edit : What is the real type of the item and query may not be iterable