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• "Dealing with uncertainty" - Entity Framework CodeOnly

  - by Simon Fox

  This is a bit of a strange one but I've just seen something on twitter which kind of baffled me and I'm interested to know more. Rob Conery tweeted the following a couple of hours ago: Class name of the day: "Maybe<T>". Method of the day: "ToMaybe<T>()". He then went on to offer a Tekpub coupon to anyone who could guess where it came from. He linked to a further tweet which had a clue and from that I worked out that it was Entity Framework Code-Only but while trying to determine the usage someone else answered to which Rob replied ...EF CodeOnly - dealing with uncertainty.... So my question boils down to what exactly is he referring to with uncertainty and how does this fit in to Entity Framework Code-Only?

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• Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures?

  - by BritishDeveloper

  How would you rate each of them in terms of: Performance Speed of development Neat, intuitive, maintainable code Flexibility Overall I like my SQL and so have always been a die-hard fan of ADO.NET and stored procedures but I recently had a play with Linq to SQL and was blown away by how quickly I was writing out my DataAccess layer and have decided to spend some time really understanding either Linq to SQL or EF... or neither? I just want to check, that there isn't a great flaw in any of these technologies that would render my research time useless. E.g. performance is terrible, it's cool for simple apps but can only take you so far

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• Mapping one to one foreign key relationships in Entity Framework 4.0?

  - by John K.

  Hello all, I'm sure I'm missing something very simple, but let's say I have two entities, Employee and EmployeeType. Employee type would contain values like 'Full time', 'Contractor', 'Intern', etc. An Employee entity would contain one, and only one EmployeeType value. So I am designing a new .edmx model using the Model-First approach and generating my actual sql server data schema from the model. I want to add an integer type foreign key id into my Employee entity, EmployeeTypeId, which will map to the primary key of the EmployeeType entity. So I've gone ahead and done that in my Employee entity. Where I'm stuck is how, though the Entity Framework designer, to enforce the 1:1 referential constraint on that EmployeeTypeId property? Or does the EF handle that automatically behind the scenes? thanks in advance, John

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• Using Sculpture with NHibernate or Entity Framework

  - by Sergei

  I recently ran across this open-source project: http://www.codeplex.com/Sculpture Sculpture is a code-generator which allows you to design your domain model and then use persistence 'molds' such as NHibernate/EF and probably more to generate repositories. It takes care of all the mapping and Data access generation. It looks like it does a heck of a lot more, but i'm pretty much sold at this point. However, i would like to know if anyone here used this for real-world solutions. If so, how well does it scale? How did the generated DAL work for you?

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• Silverlight data-driven application with NHibernate

  - by Tigraine

  Hi Guys, this is more of a subjective Question, but I'll ask it anyway. I'm about to develop a very data-centric application that has to run inside the browser. The frontend will be Silverlight, backed by a Fluent NHibernate service that runs server side. The problem here is: Wherever I look for data-driven silverlight app I wind up finding Silverlight RIA services examples, but nothing on how to build this without some ADO.NET stuff involved. I have little to no knowledge in WCF so far, but from the limited research I did it seems like WCF is pretty much the only way to let the client talk to the server. Are there any tutorials/best practices on how to write a Silverlight MVVM app that provides CRUD for a non-EF database? Suggestions would be very much appreciated. Thanks PS: I can't use .NET remoting. The backend has to run on IIS6 :(

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• How do I get a right outer join in L2E?

  - by Dan

  I have two tables that I set up through the VS Entity Data Model Diagram tool. I'm trying to do a right outer join and it doesn't return results from the 2nd table. I have set up a 0..1 to MANY relationship from the diagram tool. When I run a Linq-To-Entities query, it still defaults to an INNER JOIN. From my understanding of entities, if I set up the relationship using VS, when I join the tables, it should automagically figure out the join syntax based on the relationship I supply. It doesn't seem to be doing that. I am using EF v1 (not Linq-to-Sql). Query I'm running: from s in SomeTable join t in SomeOtherTable on s.ID equals t.ID select new { s.MyFieldName, t.MyOtherFieldName }

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• Preventing EF4 ConstraintException when invoking TryUpdateModel

  - by twk

  Given following ASP.NET MVC controller code: [HttpPost] public ActionResult Create(FormCollection collection) { string[] whitelist = new []{ "CompanyName", "Address1", "Address2", ... }; Partner newPartner = new Partner(); if (TryUpdateModel(newPartner, whitelist, collection)) { var db = new mainEntities(); db.Partners.AddObject(newPartner); db.SaveChanges(); return RedirectToAction("Details/" + newPartner.ID); } else { return View(); } } The problem is with the Entity Framework 4: the example Partner entity is mapped to a database table with it's fields NOT ALLOWED to be NULL (which is ok by design - they're required). Unfortunately, invoking TryUpdateModel when some of the properties are nulls produces ConstraintException which is not expected! I do expect that TryUpdateModel return false in this case. It is ok that EF wouldn't allow set a property value to null if it should not be, but the TryUpdateMethod should handle that, and add the error to ModelState errors collection. I am wrong, or somebody screwed the implementation of TryUpdateModel method?

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• What's all the hype over objectsets in Entity Framework 4?

  - by Kohan

  I am an intermediate user of EF in .net 3.5 and have recently moved to working with .net 4. One thing i keep coming across when reading various tutorials is the use of ObjectSets instead of ObjectQuerys and that they are a great new feature. What is so great about them? Reading this MSDN article titled "Working with ObjectSet (Entity Framework)" It shows two examples on how to add a Product.. one for 3.5 and another for 4.0. http://msdn.microsoft.com/en-us/library/ee473442.aspx Through my lack of knowledge I am possibly bringing up a seperate point here, but i never added a Product like this: //In .NET Framework 3.5 SP1, use the following code: using (AdventureWorksEntities context = new AdventureWorksEntities()) { // Add the new object to the context. context.AddObject("Products", newProduct); } I would have just used context.AddToProducts(newProduct); Please enlighten me. Kind regards, Kohan

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• Entity Framework How to specify paramter type in generated SQL (SQLServer 2005) Nvarchar vs Varchar

  - by Gratzy

  In entity framework I have an Entity 'Client' that was generated from a database. There is a property called 'Account' it is defined in the storage model as: <Property Name="Account" Type="char" Nullable="false" MaxLength="6" /> And in the Conceptual Model as: <Property Name="Account" Type="String" Nullable="false" /> When select statements are generated using a variable for Account i.e. where m.Account == myAccount... Entity Framework generates a paramaterized query with a paramater of type NVarchar(6). The problem is that the column in the table is data type of char(6). When this is executed there is a large performance hit because of the data type difference. Account is an index on the table and instead of using the index I believe an Index scan is done. Anyone know how to force EF to not use Unicode for the paramater and use Varchar(6) instead?

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• EF4 - What's all the hype over objectsets?

  - by Kohan

  I am an intermediate user of EF in .net 3.5 and have recently moved to working with .net 4. One think i keep coming across when reading various tutorials is the use of ObjectSets instead of ObjectQuerys and that they are a great new feature. What is so great about them? Reading this MSDN article titled "Working with ObjectSet (Entity Framework)" It shows two examples for on how to add a Product.. one for 3.5 and another for 4.0. http://msdn.microsoft.com/en-us/library/ee473442.aspx Though my lack of knowledge I am possibly bringing up a seperate point here, but i never added a Product like this: //In .NET Framework 3.5 SP1, use the following code: using (AdventureWorksEntities context = new AdventureWorksEntities()) { // Add the new object to the context. context.AddObject("Products", newProduct); } I would have just used context.AddToProducts(newProduct); Please enlighten me. Kind regards, Kohan

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• Automapping to EntityKeys in Entity Framework

  - by CodeGrue

  Does anyone have a technique to automap (using Automapper) references to child entities. So say I have a ViewModel: class AddressModel { int Id; string Street; StateModel State; } class StateModel { int Id; string Name; } And I pass this into a repository to map to equivalent entities in Entity Framework. When Automapping, I want it to automap AddressModel.State.ID to the EntityKey of AddressEntity.StateReference. So hand crafted code would look like this: addressEntity.Id = AddressModel.Id; addressEntity.Street = AddressModel.Street addressEntity.StateReference.EntityKey = new EntityKey("MyDB.States", "Id", AddressModel.State.Id); Obviously, when automapper tries to assign an Address.State.Id to the equivalent in EF, an exception is thrown.

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• Generic Any/Attach/Add function for Entity Framework

  - by Matt Thrower

  Looking through my EF classes, they're littered with code that looks like this: if (_myContext.[EntityType].Any(d => d.RowId == dc.RowId)) { _myContext.[EntityType].Attach(dc); _myContext.Entry(dc).State = EntityState.Modified; } else { _myContext.[EntityType].Add(dc); } It's the same thing over and over, and is clearly itching to be handled by a generic function. However, I'm not sure how you'd go about handling the need for it to deal with a variety of unexpected entity types. A good example to get me started would be most appreciated.

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• Entity Framework query builder methods: why "it" and not lambdas?

  - by nlawalker

  I'm just getting started with EF and a query like the following strikes me as odd: var departmentQuery = schoolContext.Departments.Include("Courses"). OrderBy("it.Name"); Specifically, what sticks out to me is "it.Name." When I was tooling around with LINQ to SQL, pretty much every filter in a query-builder query could be specified with a lambda, like, in this case, d = d.Name. I see that there are overrides of OrderBy that take lambdas that return an IOrderedQueryable or an IOrderedEnumable, but those obviously don't have the Execute method needed to get the ObjectResult that can then be databound. It seems strange to me after all I've read about how lambdas make so much sense for this kind of stuff, and how they are translated into expression trees and then to a target language - why do I need to use "it.Name"?

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• Ado.Net Entity produces "namespace cannot be found"

  - by Dave

  I've seen several possible solutions to this, but none have worked for me. After adding a ADO.NET Entity Data Model to my .Net Forms C# web project, I am unable to use it. Perhaps I made a mistake adding it? The name of the file added is QcFormData.edmx. In my code, perhaps I'm instantiating it incorrectly? I tried adding the line: QcFormDataContainer db = new QcFormDataContainer(); It appears in Intellisense, but when compiling I get the error : Error 13 The type or namespace name 'QcFormDataContainer' could not be found (are you missing a using directive or an assembly reference?) I've followed the suggestions that I found online that did not help: 1) made sure there is "using System.Data.Entity" 2) made sure the dll exists. 3) made sure the reference exists. 4) one post said use using System.Web.Data.Entity; but I do not see that available. What am I missing? QcFormData.edmx <?xml version="1.0" encoding="utf-8"?> <edmx:Edmx Version="3.0" xmlns:edmx="http://schemas.microsoft.com/ado/2009/11/edmx"> <!-- EF Runtime content --> <edmx:Runtime> <!-- SSDL content --> <edmx:StorageModels> <Schema Namespace="MyCocoModel.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2008" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns="http://schemas.microsoft.com/ado/2009/11/edm/ssdl"> <EntityContainer Name="MyCocoModelStoreContainer"> <EntitySet Name="QcFieldValues" EntityType="MyCocoModel.Store.QcFieldValues" store:Type="Tables" Schema="dbo" /> </EntityContainer> <EntityType Name="QcFieldValues"> <Key> <PropertyRef Name="ID" /> </Key> <Property Name="ID" Type="int" Nullable="false" StoreGeneratedPattern="Identity" /> <Property Name="FieldID" Type="nvarchar" MaxLength="100" /> <Property Name="FieldValue" Type="nvarchar" MaxLength="100" /> <Property Name="DateTimeAdded" Type="datetime" /> <Property Name="OrderReserveNumber" Type="nvarchar" MaxLength="50" /> </EntityType> </Schema> </edmx:StorageModels> <!-- CSDL content --> <edmx:ConceptualModels> <Schema Namespace="MyCocoModel" Alias="Self" p1:UseStrongSpatialTypes="false" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns:p1="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns="http://schemas.microsoft.com/ado/2009/11/edm"> <EntityContainer Name="MyCocoEntities" p1:LazyLoadingEnabled="true"> <EntitySet Name="QcFieldValues" EntityType="MyCocoModel.QcFieldValue" /> </EntityContainer> <EntityType Name="QcFieldValue"> <Key> <PropertyRef Name="ID" /> </Key> <Property Name="ID" Type="Int32" Nullable="false" p1:StoreGeneratedPattern="Identity" /> <Property Name="FieldID" Type="String" MaxLength="100" Unicode="true" FixedLength="false" /> <Property Name="FieldValue" Type="String" MaxLength="100" Unicode="true" FixedLength="false" /> <Property Name="DateTimeAdded" Type="DateTime" Precision="3" /> <Property Name="OrderReserveNumber" Type="String" MaxLength="50" Unicode="true" FixedLength="false" /> </EntityType> </Schema> </edmx:ConceptualModels> <!-- C-S mapping content --> <edmx:Mappings> <Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2009/11/mapping/cs"> <EntityContainerMapping StorageEntityContainer="MyCocoModelStoreContainer" CdmEntityContainer="MyCocoEntities"> <EntitySetMapping Name="QcFieldValues"> <EntityTypeMapping TypeName="MyCocoModel.QcFieldValue"> <MappingFragment StoreEntitySet="QcFieldValues"> <ScalarProperty Name="ID" ColumnName="ID" /> <ScalarProperty Name="FieldID" ColumnName="FieldID" /> <ScalarProperty Name="FieldValue" ColumnName="FieldValue" /> <ScalarProperty Name="DateTimeAdded" ColumnName="DateTimeAdded" /> <ScalarProperty Name="OrderReserveNumber" ColumnName="OrderReserveNumber" /> </MappingFragment> </EntityTypeMapping> </EntitySetMapping> </EntityContainerMapping> </Mapping> </edmx:Mappings> </edmx:Runtime> <!-- EF Designer content (DO NOT EDIT MANUALLY BELOW HERE) --> <Designer xmlns="http://schemas.microsoft.com/ado/2009/11/edmx"> <Connection> <DesignerInfoPropertySet> <DesignerProperty Name="MetadataArtifactProcessing" Value="EmbedInOutputAssembly" /> </DesignerInfoPropertySet> </Connection> <Options> <DesignerInfoPropertySet> <DesignerProperty Name="ValidateOnBuild" Value="true" /> <DesignerProperty Name="EnablePluralization" Value="True" /> <DesignerProperty Name="IncludeForeignKeysInModel" Value="True" /> <DesignerProperty Name="CodeGenerationStrategy" Value="None" /> </DesignerInfoPropertySet> </Options> <!-- Diagram content (shape and connector positions) --> <Diagrams></Diagrams> </Designer> </edmx:Edmx>

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• EntityFramework & RowNumber

  - by Dan

  Hello. How can I query RowNumber with Entity Framework? For example: var result = data.Users .OrderByDescending("Birthday") .ThenBy("LastName") .ThenBy("FirstName") .Select(u => { RowNumber = ???, u.FirstName, u.LastName }); I want to implement paging for my grid, but I cannot solve problem with finding page with needed user. I'm using EF4.0. Select method with index(http://msdn.microsoft.com/en-us/vcsharp/aa336758.aspx#SelectIndexed) not works with EF. May be there is another way to implement this?

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• Retrieve entities with children per one sql call. ADO.NET Entity framework

  - by Andrew Florko

  Hello everybody, I have two tables: A & B B { B1: Field1, B2: Field2, ... } A { Children: List of B, A1: Field1, A2: Field2, } I want to retrieve "A" entities with related "B" entities like this: DataContext.A.Select( a = new MySubset( A1 = a.A1, Children = a.Children.Select(b = b.B1).ToList()); But EF can't translate ToList into SQL, so i have to call ToList() per each instance in query producing additional network call. How can I avoid this? Thank you in advance.

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• Trying to connect internally to Oracle, getting an idle instance?

  - by seanbseanbseanbseanb

  So I have an Oracle instance, and I know it's running on this system, I've su'd to the oracle user, and I'm trying to connect using "/ as sysdba". However, when I do connect, it says the instance is idle. I know the database is up and opened, because my application's talking to it. My paths (ORACLE_HOME, etc.) might be incorrect: any idea which incorrect setting might result in this? % sqlplus "/ as sysdba" SQL*Plus: Release 10.2.0.3.0 - Production on Mon Dec 8 09:23:22 2008 Copyright (c) 1982, 2006, Oracle. All Rights Reserved. Connected to an idle instance. 09:23:22 SQL Disconnected % ps -ef | grep smon oracle 6961 1 0 Nov 05 ? 1:24 ora_smon_ORA003 %

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• What are some "mental steps" a developer must take to begin moving from SQL to NO-SQL (CouchDB, Fath

  - by Byron Sommardahl

  I have my mind firmly wrapped around relational databases and how to code efficiently against them. Most of my experience is with MySQL and SQL. I like many of the things I'm hearing about document-based databases, especially when someone in a recent podcast mentioned huge performance benefits. So, if I'm going to go down that road, what are some of the mental steps I must take to shift from SQL to NO-SQL? If it makes any difference in your answer, I'm a C# developer primarily (today, anyhow). I'm used to ORM's like EF and Linq to SQL. Before ORMs, I rolled my own objects with generics and datareaders. Maybe that matters, maybe it doesn't. Here are some more specific: How do I need to think about joins? How will I query without a SELECT statement? What happens to my existing stored objects when I add a property in my code? (feel free to add questions of your own here)

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• EntityFramework gives IDisposable error

  - by Snoop Dogg

  I use EF for the back-end DataLayer in my asp.net websites. I create a class library and add the Model in it, reference it and use it from the ASP.NET Website. But this time, I generated the model from database but it seems does not implement IDisposable, and the methods I used to see are not there. DeleteObject , SaveChanges etc. There are only Two tables in the DB and the Model was generated with only the TableSets and two methods AddToTableSet ... Had anybody encountered such a problem?

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• Do I need to include all fields in my entity framework model

  - by Jim B

  Quick question for everyone: Do I need to include all the database table fields on my EF model? For example; I've created a sub-model that only deals with tblPayment and associated tables. Now, I need to write a LINQ query to get some information about items. I would typically get this by joining tblPayment to tblInvoice to tblInvoiceItem to finally tblOrderItem. I'm wondering if when I add in those other tables, do I need to include all the fields for tblInvoice and tblInvoiceItem? Ideally; I'd just like to keep the fields I'd need to join on, as that would limit the possibility of my sub-model breaking if other fields on those tables are modified/deleted. Can I do this?

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• how to populate an entity you have extended in the Entity Framework?

  - by user169867

  I have an entity in my EDMX that I've extended with a few fields in a partial class like this: public partial class Employee { public string JobName {get;set;} } These properties are for display only. In the above example say the entity has a JobTypeID property. I wish JobName to be populated w/ the name that belongs to that JobTypeID. Is there anyway to query the employee record in EF including the value for the JobName property w/o explicity assigning each field using select()? The reason I ask is that there are a lot of fields in the Employee entity so I'd like to be able to take advantage of something like: ctx.Employees.Where(e=>e.EmployeeID==employeeID).Single() ...add somehow fill in JobName too Is this possible?

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• entity framework and dirty reads

  - by bryanjonker

  I have Entity Framework (.NET 4.0) going against SQL Server 2008. The database is (theoretically) getting updated during business hours -- delete, then insert, all through a transaction. Practically, it's not going to happen that often. But, I need to make sure I can always read data in the database. The application I'm writing will never do any types of writes to the data -- read-only. If I do a dirty read, I can always access the data; the worst that happens is I get old data (which is acceptable). However, can I tell Entity Framework to always use dirty reads? Are there performance or data integrity issues I need to worry about if I set up EF this way? Or should I take a step back and see about rewriting the process that's doing the delete/insert process?

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• Entity Framework model and foreign key property

  - by verror

  I have 2 tables that I import to EF model. First table has a property [section] that acts as foreign key to the second table. When I map this property in model to the table and try to compile I get this error: Problem in Mapping Fragments starting at lines 158, 174: Non-Primary-Key column(s) [Section] are being mapped in both fragments to different conceptual side properties - data inconsistency is possible because the corresponding conceptual side properties can be independently modified. If i remove this property from the model it passes, but when I query the data I don't have the section field. I know that I can get it by using the navigation field and reading this property from the second table, but to make it work I must include the other table in my query. var res = from name in Context.Table1.Include("Table2")... Why do I need to include the association just for one field?

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• Get Average Using LINQ

  - by obautista

  Hoping someone can help me with the LINQ syntax to calculate an average. For example, I have the following LINQ query: var rates = from rating in ctx.Rates where rating.Id == Id select new { UserId = rating.UserId, Rating = rating.Rating }; If 10 records are returned, I need to calculate average on the Rating field. It is defined as as a Double in my DB. I am using LINQ to EF. So I would be assigning the UserId, MiscId, and the Rating would be the average on the records returned. I am passing one object back to the client code.

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• How can I evaluate a deferred Linq statement when debugging?

  - by DanO

  I'm debugging in VS2010, and I want to inspect a string value but all I can get the debugger to show me (through watches, hovering, locals, etc.) is: "System.Linq.Enumerable+<TakeIterator>d__3a`1[System.Char]" I don't care if there are side effects from premature evaluation or whatever, I just want to see what the expression would evaluate to if I evaluate it right now at the current breakpoint. How is this done? Also can I change my code in such a way that it evaluates earlier? Not that I care when I'm not debugging... but just wondering. In case it is relevant... (I doubt it.) I'm stuffing a new entity object before saving it to the database... some fields are assigned with LINQ statements, I'm not sure when they get evaluated under the covers of EF. The DB update fails with 'string or binary data would be truncated... So I'm trying to find the too-long field.

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