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  • Alternatives to the Entity Framework for Serving/Consuming an OData Interface

    - by Egahn
    I'm researching how to set up an OData interface to our database. I would like to be able to pull/query data from our DB into Excel, as a start. Eventually I would like to have Excel run queries and pull data over HTTP from a remote client, including authentication, etc. I've set up a working (rickety) prototype so far, using the ADO.NET Entity Data Model wizard in Visual Studio, and VSTO to create a test Excel worksheet with a button to pull from that ADO.NET interface. This works OK so far, and I can query the DB using Linq through the entities/objects that are created by the ADO.NET EDM wizard. However, I have started to run into some problems with this approach. I've been finding the Entity Framework difficult to work with (and in fact, also difficult to research solutions to, as there's a lot of chaff out there regarding it and older versions of it). An example of this is my being unable to figure out how to set the SQL command timeout (as opposed to the HTTP request timeout) on the DataServiceContext object that the wizard generates for my schema, but that's not the point of my question. The real question I have is, if I want to use OData as my interface standard, am I stuck with the Entity Framework? Are there any other solutions out there (preferably open source) which can set up, serve and consume an OData interface, and are easier to work with and less bloated than the Entity Framework? I have seen mention of NHibernate as an alternative, but most of the comparison threads I've seen are a few years old. Are there any other alternatives out there now? Thanks very much!

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  • Entity Framework 4 + POCO with custom classes and WCF contracts (serialization problem)

    - by eman
    Yesterday I worked on a project where I upgraded to Entity Framework 4 with the Repository pattern. In one post, I have read that it is necessary to turn off the custom tool generator classes and then write classes (same like entites) by hand. That I can do it, I used the POCO Entity Generator and then deleted the new generated files .tt and all subordinate .cs classes. Then I wrote the "entity classes" by myself. I added the repository pattern and implemented it in the business layer and then implemented a WCF layer, which should call the methods from the business layer. By calling an Insert (Add) method from the presentation layer and everything is OK. But if I call any method that should return some class, then I get an error like (the connection was interrupted by the server). I suppose there is a problem with the serialization or am I wrong? How can by this problem solved? I'm using Visual Studio S2010, Entity Framework 4, C#. UPDATE: I have uploaded the project and hope somebody can help me! link text UPDATE 2: My questions: Why is POCO good (pros/cons)? When should POCO be used? Is POCO + the repository pattern a good choice? Should POCO classes by written by myself or could I use auto generated POCO classes?

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  • Strange JPA one-to-many behavior when trying to set the "many" on the "one" entity

    - by errr
    I've mapped two entities using JPA (specifically Hibernate). Those entities have a one-to-many relationship (I've simplified for presentation): @Entity public class A { @ManyToOne public B getB() { return b; } } @Entity public Class B { @OneToMany(mappedBy="b") public Set<A> getAs() { return as; } } Now, I'm trying to create a relationship between two instances of these entities by using the setter of the one-side/not-owner-side of the relationship (i.e the table being referenced to): em.getTransaction().begin(); A a = new A(); B b = new B(); Set<A> as = new HashSet<A>(); as.add(a); b.setAs(as); em.persist(a); em.persist(b); em.getTransaction().commit(); But then, the relationship isn't persisted to the DB (the row created for entity A isn't referencing the row created for entity B). Why is it so? I'd excpect it to work. Also, if I remove the "mappedBy" property from the @OneToMany annotation it will work. Again - why is it so? and what are the possible effects for removing the "mappedBy" property?

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  • Prroblem with ObjectDelete() in Entity Framework 4

    - by Tom
    I got two entities: public class User : Entity { public virtual string Username { get; set; } public virtual string Email { get; set; } public virtual string PasswordHash { get; set; } public virtual List<Photo> Photos { get; set; } } and public class Photo : Entity { public virtual string FileName { get; set; } public virtual string Thumbnail { get; set; } public virtual string Description { get; set; } public virtual int UserId { get; set; } public virtual User User { get; set; } } When I try to delete the photo it works fine for the DB (record gets romoved from the table) but it doesnt for the Photos collection in the User entity (I can still see that photo in user.Photos). This is my code. What I'm doing wrong here? Changing entity properties works fine. When I change photo FileName for example it gets updated in DB and in user.Photos. var photo = SelectById(id); Context.DeleteObject(photo); Context.SaveChanges(); var user = GetUser(userName); // the photo I have just deleted is still in user.Photos also tried this but getting same results: var photo = user.Photos.First(); Context.DeleteObject(photo); Context.SaveChanges();

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  • ReflectionTypeLoadException when I try to run Enable-Migrations with Entity Framework 5.0

    - by Eric Anastas
    I'm trying to use Entity Framework for the first time on one of my projects. I'm using the code first workflow to automatically create my database. Intitaly setting up the database worked fine. Now I'm trying to migrate changes in my classes into the database. The tutorial I'm reading says I need to run "Enable-Migrations" in the package manager console. Yet when I do this I get the following error PM> Enable-Migrations System.Reflection.ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. at System.Reflection.RuntimeModule.GetTypes(RuntimeModule module) at System.Reflection.RuntimeModule.GetTypes() at System.Reflection.Assembly.GetTypes() at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.FindType[TBase](String typeName, Func`2 filter, Func`2 noType, Func`3 multipleTypes, Func`3 noTypeWithName, Func`3 multipleTypesWithName) at System.Data.Entity.Migrations.Design.ToolingFacade.GetContextTypeRunner.RunCore() at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run() Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. What am I doing wrong? How do I retrieve the loader exceptions property? Also NuGet says I have EF 5.0, but Version property of the EntityFramework item in my project references says 4.4.0.0. I'm not sure if this is related.

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  • Entity framework self referencing loop detected

    - by Lyd0n
    I have a strange error. I'm experimenting with a .NET 4.5 Web API, Entity Framework and MS SQL Server. I've already created the database and set up the correct primary and foreign keys and relationships. I've created a .edmx model and imported two tables: Employee and Department. A department can have many employees and this relationship exists. I created a new controller called EmployeeController using the scaffolding options to create an API controller with read/write actions using Entity Framework. In the wizard, selected Employee as the model and the correct entity for the data context. The method that is created looks like this: // GET api/Employee public IEnumerable<Employee> GetEmployees() { var employees = db.Employees.Include(e => e.Department); return employees.AsEnumerable(); } When I call my API via /api/Employee, I get this error: ...The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; ...System.InvalidOperationException","StackTrace":null,"InnerException":{"Message":"An error has occurred.","ExceptionMessage":"Self referencing loop detected with type 'System.Data.Entity.DynamicProxies.Employee_5D80AD978BC68A1D8BD675852F94E8B550F4CB150ADB8649E8998B7F95422552'. Path '[0].Department.Employees'.","ExceptionType":"Newtonsoft.Json.JsonSerializationException","StackTrace":" ... Why is it self referencing [0].Department.Employees? That doesn't make a whole lot of sense. I would expect this to happen if I had circular referencing in my database but this is a very simple example. What could be going wrong?

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  • Entity Framework 4, WCF &amp; Lazy Loading Tip

    - by Dane Morgridge
    If you are doing any work with Entity Framework and custom WCF services in EFv1, everything works great.  As soon as you jump to EFv4, you may find yourself getting odd errors that you can’t seem to catch.  The problem is almost always has something to do with the new lazy loading feature in Entity Framework 4.  With Entity Framework 1, you didn’t have lazy loading so this problem didn’t surface.  Assume I have a Person entity and an Address entity where there is a one-to-many relationship between Person and Address (Person has many Addresses). In Entity Framework 1 (or in EFv4 with lazy loading turned off), I would have to load the Address data by hand by either using the Include or Load Method: var people = context.People.Include("Addresses"); or people.Addresses.Load(); Lazy loading works when the first time the Person.Addresses collection is accessed: 1: var people = context.People.ToList(); 2:  3: // only person data is currently in memory 4:  5: foreach(var person in people) 6: { 7: // EF determines that no Address data has been loaded and lazy loads 8: int count = person.Addresses.Count(); 9: } 10:  Lazy loading has the useful (and sometimes not useful) feature of fetching data when requested.  It can make your life easier or it can make it a big pain.  So what does this have to do with WCF?  One word: Serialization. When you need to pass data over the wire with WCF, the data contract is serialized into either XML or binary depending on the binding you are using.  Well, if I am using lazy loading, the Person entity gets serialized and during that process, the Addresses collection is accessed.  When that happens, the Address data is lazy loaded.  Then the Address is serialized, and the Person property is accessed, and then also serialized and then the Addresses collection is accessed.  Now the second time through, lazy loading doesn’t kick in, but you can see the infinite loop caused by this process.  This is a problem with any serialization, but I personally found it trying to use WCF. The fix for this is to simply turn off lazy Loading.  This can be done at each call by using context options: context.ContextOptions.LazyLoadingEnabled = false; Turning lazy loading off will now allow your classes to be serialized properly.  Note, this is if you are using the standard Entity Framework classes.  If you are using POCO,  you will have to do something slightly different.  With POCO, the Entity Framework will create proxy classes by default that allow things like lazy loading to work with POCO.  This proxy basically creates a proxy object that is a full Entity Framework object that sits between the context and the POCO object.  When using POCO with WCF (or any serialization) just turning off lazy loading doesn’t cut it.  You have to turn off the proxy creation to ensure that your classes will serialize properly: context.ContextOptions.ProxyCreationEnabled = false; The nice thing is that you can do this on a call-by-call basis.  If you use a new context for each set of operations (which you should) then you can turn either lazy loading or proxy creation on and off as needed.

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  • Upgraded to EF6 blew up Universal provider session state for Azure

    - by Ryan
    I have an ASP.NET MVC 4 application that using the Universal providers for session state: <sessionState mode="Custom" sqlConnectionString="DefaultConnection" customProvider="DefaultSessionProvider"> <providers> <add name="DefaultSessionProvider" type="System.Web.Providers.DefaultSessionStateProvider, System.Web.Providers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" connectionStringName="DefaultConnection" /> </providers> </sessionState> When I upgraded to entity framework 6 I now get this error: Method not found: 'System.Data.Objects.ObjectContext System.Data.Entity.Infrastructure.IObjectContextAdapter.get_ObjectContext()'. I tried adding the reference to System.Data.Entity.dll back in but that didn't work and I know that your not suppose to add that with the new entity framework..

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  • POCO inherited type could not pass addObject method

    - by bryanevil
    Hi all I am using a POCO class name "Company" generate from the T4 POCO code generator to create a derived class - name "CompanyBO" by "public class CompanyBO:Company", but when i call addObject method: public void Delete(T entity) { CustomerWebPortalEntities entities = new CustomerWebPortalEntities(); entities.AddObject(entity.GetType().BaseType.Name, entity); entities.DeleteObject(entity); SaveChanges(); } it compliant this: The EntitySet name 'CustomerWebPortalEntities.Company' could not be found. System.Data.Objects.ObjectContext.GetEntitySet(String entitySetName, String entityContainerName) at System.Data.Objects.ObjectContext.GetEntitySetFromName(String entitySetName) Could you please tell me whats going wrong here? How do I resolve this problem? Best Regards Bryan

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  • LLBLGen Pro feature highlights: automatic element name construction

    - by FransBouma
    (This post is part of a series of posts about features of the LLBLGen Pro system) One of the things one might take for granted but which has a huge impact on the time spent in an entity modeling environment is the way the system creates names for elements out of the information provided, in short: automatic element name construction. Element names are created in both directions of modeling: database first and model first and the more names the system can create for you without you having to rename them, the better. LLBLGen Pro has a rich, fine grained system for creating element names out of the meta-data available, which I'll describe more in detail below. First the model element related element naming features are highlighted, in the section Automatic model element naming features and after that I'll go more into detail about the relational model element naming features LLBLGen Pro has to offer in the section Automatic relational model element naming features. Automatic model element naming features When working database first, the element names in the model, e.g. entity names, entity field names and so on, are in general determined from the relational model element (e.g. table, table field) they're mapped on, as the model elements are reverse engineered from these relational model elements. It doesn't take rocket science to automatically name an entity Customer if the entity was created after reverse engineering a table named Customer. It gets a little trickier when the entity which was created by reverse engineering a table called TBL_ORDER_LINES has to be named 'OrderLine' automatically. Automatic model element naming also takes into effect with model first development, where some settings are used to provide you with a default name, e.g. in the case of navigator name creation when you create a new relationship. The features below are available to you in the Project Settings. Open Project Settings on a loaded project and navigate to Conventions -> Element Name Construction. Strippers! The above example 'TBL_ORDER_LINES' shows that some parts of the table name might not be needed for name creation, in this case the 'TBL_' prefix. Some 'brilliant' DBAs even add suffixes to table names, fragments you might not want to appear in the entity names. LLBLGen Pro offers you to define both prefix and suffix fragments to strip off of table, view, stored procedure, parameter, table field and view field names. In the example above, the fragment 'TBL_' is a good candidate for such a strip pattern. You can specify more than one pattern for e.g. the table prefix strip pattern, so even a really messy schema can still be used to produce clean names. Underscores Be Gone Another thing you might get rid of are underscores. After all, most naming schemes for entities and their classes use PasCal casing rules and don't allow for underscores to appear. LLBLGen Pro can automatically strip out underscores for you. It's an optional feature, so if you like the underscores, you're not forced to see them go: LLBLGen Pro will leave them alone when ordered to to so. PasCal everywhere... or not, your call LLBLGen Pro can automatically PasCal case names on word breaks. It determines word breaks in a couple of ways: a space marks a word break, an underscore marks a word break and a case difference marks a word break. It will remove spaces in all cases, and based on the underscore removal setting, keep or remove the underscores, and upper-case the first character of a word break fragment, and lower case the rest. Say, we keep the defaults, which is remove underscores and PasCal case always and strip the TBL_ fragment, we get with our example TBL_ORDER_LINES, after stripping TBL_ from the table name two word fragments: ORDER and LINES. The underscores are removed, the first character of each fragment is upper-cased, the rest lower-cased, so this results in OrderLines. Almost there! Pluralization and Singularization In general entity names are singular, like Customer or OrderLine so LLBLGen Pro offers a way to singularize the names. This will convert OrderLines, the result we got after the PasCal casing functionality, into OrderLine, exactly what we're after. Show me the patterns! There are other situations in which you want more flexibility. Say, you have an entity Customer and an entity Order and there's a foreign key constraint defined from the target of Order and the target of Customer. This foreign key constraint results in a 1:n relationship between the entities Customer and Order. A relationship has navigators mapped onto the relationship in both entities the relationship is between. For this particular relationship we'd like to have Customer as navigator in Order and Orders as navigator in Customer, so the relationship becomes Customer.Orders 1:n Order.Customer. To control the naming of these navigators for the various relationship types, LLBLGen Pro defines a set of patterns which allow you, using macros, to define how the auto-created navigator names will look like. For example, if you rather have Customer.OrderCollection, you can do so, by changing the pattern from {$EndEntityName$P} to {$EndEntityName}Collection. The $P directive makes sure the name is pluralized, which is not what you want if you're going for <EntityName>Collection, hence it's removed. When working model first, it's a given you'll create foreign key fields along the way when you define relationships. For example, you've defined two entities: Customer and Order, and they have their fields setup properly. Now you want to define a relationship between them. This will automatically create a foreign key field in the Order entity, which reflects the value of the PK field in Customer. (No worries if you hate the foreign key fields in your classes, on NHibernate and EF these can be hidden in the generated code if you want to). A specific pattern is available for you to direct LLBLGen Pro how to name this foreign key field. For example, if all your entities have Id as PK field, you might want to have a different name than Id as foreign key field. In our Customer - Order example, you might want to have CustomerId instead as foreign key name in Order. The pattern for foreign key fields gives you that freedom. Abbreviations... make sense of OrdNr and friends I already described word breaks in the PasCal casing paragraph, how they're used for the PasCal casing in the constructed name. Word breaks are used for another neat feature LLBLGen Pro has to offer: abbreviation support. Burt, your friendly DBA in the dungeons below the office has a hate-hate relationship with his keyboard: he can't stand it: typing is something he avoids like the plague. This has resulted in tables and fields which have names which are very short, but also very unreadable. Example: our TBL_ORDER_LINES example has a lovely field called ORD_NR. What you would like to see in your fancy new OrderLine entity mapped onto this table is a field called OrderNumber, not a field called OrdNr. What you also like is to not have to rename that field manually. There are better things to do with your time, after all. LLBLGen Pro has you covered. All it takes is to define some abbreviation - full word pairs and during reverse engineering model elements from tables/views, LLBLGen Pro will take care of the rest. For the ORD_NR field, you need two values: ORD as abbreviation and Order as full word, and NR as abbreviation and Number as full word. LLBLGen Pro will now convert every word fragment found with the word breaks which matches an abbreviation to the given full word. They're case sensitive and can be found in the Project Settings: Navigate to Conventions -> Element Name Construction -> Abbreviations. Automatic relational model element naming features Not everyone works database first: it may very well be the case you start from scratch, or have to add additional tables to an existing database. For these situations, it's key you have the flexibility that you can control the created table names and table fields without any work: let the designer create these names based on the entity model you defined and a set of rules. LLBLGen Pro offers several features in this area, which are described in more detail below. These features are found in Project Settings: navigate to Conventions -> Model First Development. Underscores, welcome back! Not every database is case insensitive, and not every organization requires PasCal cased table/field names, some demand all lower or all uppercase names with underscores at word breaks. Say you create an entity model with an entity called OrderLine. You work with Oracle and your organization requires underscores at word breaks: a table created from OrderLine should be called ORDER_LINE. LLBLGen Pro allows you to do that: with a simple checkbox you can order LLBLGen Pro to insert an underscore at each word break for the type of database you're working with: case sensitive or case insensitive. Checking the checkbox Insert underscore at word break case insensitive dbs will let LLBLGen Pro create a table from the entity called Order_Line. Half-way there, as there are still lower case characters there and you need all caps. No worries, see below Casing directives so everyone can sleep well at night For case sensitive databases and case insensitive databases there is one setting for each of them which controls the casing of the name created from a model element (e.g. a table created from an entity definition using the auto-mapping feature). The settings can have the following values: AsProjectElement, AllUpperCase or AllLowerCase. AsProjectElement is the default, and it keeps the casing as-is. In our example, we need to get all upper case characters, so we select AllUpperCase for the setting for case sensitive databases. This will produce the name ORDER_LINE. Sequence naming after a pattern Some databases support sequences, and using model-first development it's key to have sequences, when needed, to be created automatically and if possible using a name which shows where they're used. Say you have an entity Order and you want to have the PK values be created by the database using a sequence. The database you're using supports sequences (e.g. Oracle) and as you want all numeric PK fields to be sequenced, you have enabled this by the setting Auto assign sequences to integer pks. When you're using LLBLGen Pro's auto-map feature, to create new tables and constraints from the model, it will create a new table, ORDER, based on your settings I previously discussed above, with a PK field ID and it also creates a sequence, SEQ_ORDER, which is auto-assigns to the ID field mapping. The name of the sequence is created by using a pattern, defined in the Model First Development setting Sequence pattern, which uses plain text and macros like with the other patterns previously discussed. Grouping and schemas When you start from scratch, and you're working model first, the tables created by LLBLGen Pro will be in a catalog and / or schema created by LLBLGen Pro as well. If you use LLBLGen Pro's grouping feature, which allows you to group entities and other model elements into groups in the project (described in a future blog post), you might want to have that group name reflected in the schema name the targets of the model elements are in. Say you have a model with a group CRM and a group HRM, both with entities unique for these groups, e.g. Employee in HRM, Customer in CRM. When auto-mapping this model to create tables, you might want to have the table created for Employee in the HRM schema but the table created for Customer in the CRM schema. LLBLGen Pro will do just that when you check the setting Set schema name after group name to true (default). This gives you total control over where what is placed in the database from your model. But I want plural table names... and TBL_ prefixes! For now we follow best practices which suggest singular table names and no prefixes/suffixes for names. Of course that won't keep everyone happy, so we're looking into making it possible to have that in a future version. Conclusion LLBLGen Pro offers a variety of options to let the modeling system do as much work for you as possible. Hopefully you enjoyed this little highlight post and that it has given you new insights in the smaller features available to you in LLBLGen Pro, ones you might not have thought off in the first place. Enjoy!

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  • Entity Framework and consuming a WCF service

    - by nakori
    I'm getting data where the database is hidden behind a WCF service. Is it possible to use Entity Framework in a scenario where I have custom objects coming from a web service? (No access to the external database, and no current plans for insert/update/delete logic) Starting with an empty EF model and adding an entity I get this error on compile: No mapping specified for instances of the EntitySet and AssociationSet in the EntityContainer .. Is it possible to make an entity this way, and fill it with data received from an object? (In this case a WCF, but could also be a predefined model class/xml data) If the web service retured a Customer object I could do something like this with a dataset: Make an unbound table and do a loop through the customer properties adding them to a temp row, add it with tbl_Customer.Addtbl_CustomerRow(customerRow) to get my view filled. thanks, nakori

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  • Generate POCO classes in different project to the project with Entity Framework model

    - by Max
    I'm trying to use the Repository Pattern with EF4 using VS2010. To this end I am using POCO code generation by right clicking on the entity model designer and clicking Add code generation item. I then select the POCO template and get my classes. What I would like to be able to do is have my solution structured into separate projects for Entity (POCO) classes and another project for the entity model and repository code. This means that my MVC project could use the POCO classes for strongly typed views etc and not have to know about the repository or have to have a reference to it. To plug it all together I will have another separate project with interfaces and use IoC. Sounds good in my head I just don't know how to generate the classes into their own project! I can copy them and then change the namespaces on them but I wanted to avoid manual work whenever I change the schema in the db and want to update my model. Thanks

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  • Does Sandcastle support Entity Framework Partial Classes?

    - by ChrisHDog
    I am attempting to use Sandcastle (and Sandcastle Help File Builder) to do some "auto-documentation" of some classes I am using. The classes that are giving me trouble are some partial classes on Entity Framework items that add methods and properties to those Framework items. The triple slash comments don't appear to come through on the methods and properties created in the partial classes. I have out how to get xml documentation of the base properties using the short summary and long description fields on the .emdx editor, but that doesn't provide a solution for the items in the partial classes. Is this possible? Is it perhaps just settings that I'm not setting correctly to pick up the partial classes? Does Sandcastle do partial classes in non-Entity Framework settings? Is what I'm doing even possible (has anyone else successfully used the xml created from triple slash comments to create documentation on entity framework partial classes, and if so how did you do that)? Any assistance is appreciated

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  • Entity Framework, full-text search and temporary tables

    - by markus
    I have a LINQ-2-Entity query builder, nesting different kinds of Where clauses depending on a fairly complex search form. Works great so far. Now I need to use a SQL Server fulltext search index in some of my queries. Is there any chance to add the search term directly to the LINQ query, and have the score available as a selectable property? If not, I could write a stored procedure to load a list of all row IDs matching the full-text search criteria, and then use a LINQ-2-Entity query to load the detail data and evaluate other optional filter criteria in a loop per row. That would be of course a very bad idea performance-wise. Another option would be to use a stored procedure to insert all row IDs matching the full-text search into a temporary table, and then let the LINQ query join the temporary table. Question is: how to join a temporary table in a LINQ query, as it cannot be part of the entity model?

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  • Creating a castable entity class wrapper

    - by Tony
    Hi I need to have a wrapper class that exposes some properties of my entity class called ProfileEntity. I tried doing it by deriving from this entity and then creating properties that return specific entity properties, but it says I cannot cast from ProfileEntity to ProfileEntityWrapper. When I try to put the return values of a method that returns a 'ProfileEntity' into the wrapper I get the above error. How do I create such a wrapper class that is castable? Example class ProfileEntityWrapper : ProfileEntity { public string Name { get { return this.ProfileEntityName; } } public class Someclass { public ProfileEntity SomeMethod() { return ProfileEntity; // example of method returning this object } } public class SomeOtherlClass { SomeClass sc = new SomeClass(); public void DoSomething() { ProfileEntityWrapper ew = (ProfileEntityWrapper)sc.SomeMethod(); // Cannot do this cast!!! } }

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  • What is the proper way to create a recursive entity in the Entity Framework?

    - by Orion Adrian
    I'm currently using VS 2010 RC, and I'm trying to create a model that contains a recursive self-referencing entity. Currently when I import the entity from the model I get an error indicating that the parent property cannot be part of the association because it's set to 'Computed' or 'Identity', though I'm not sure why it does it that way. I've been hand-editing the file to get around that error, but then the model simply doesn't work. What is the proper way to get recursive entities to work in the Entity Framework. CREATE TABLE [dbo].[Appointments]( [AppointmentId] [int] IDENTITY(1,1) NOT NULL, [Description] [nvarchar](1024) NULL, [Start] [datetime] NOT NULL, [End] [datetime] NOT NULL, [Username] [varchar](50) NOT NULL, [RecurrenceRule] [nvarchar](1024) NULL, [RecurrenceState] [varchar](20) NULL, [RecurrenceParentId] [int] NULL, [Annotations] [nvarchar](50) NULL, [Application] [nvarchar](100) NOT NULL, CONSTRAINT [PK_Appointments] PRIMARY KEY CLUSTERED ( [AppointmentId] ASC ) ) GO ALTER TABLE [dbo].[Appointments] WITH CHECK ADD CONSTRAINT [FK_Appointments_ParentAppointments] FOREIGN KEY([RecurrenceParentId]) REFERENCES [dbo].[Appointments] ([AppointmentId]) GO ALTER TABLE [dbo].[Appointments] CHECK CONSTRAINT [FK_Appointments_ParentAppointments] GO

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  • How do I delete a child entity from a parent collection with Entity Framework 4?

    - by simonjreid
    I'm using Entity Framework 4 and have a one-to-many relationship between a parent and child entity. I'm trying to delete a child using the parent repository by removing it from the parent's children collection: public virtual void RemoveChild(Child child) { children.Remove(child); } When I try to save the changes I get the following error: A relationship from the 'ParentChild' AssociationSet is in the 'Deleted' state. Given multiplicity constraints, a corresponding 'Child' must also in the 'Deleted' state. Surely I don't have to delete the child entity explicitly using a child repository!

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  • Entity Framework vs LINQ to SQL

    - by Chris Roberts
    Now that .NET v3.5 SP1 has been released (along with VS2008 SP1), we now have access to the .NET entity framework. My question is this. When trying to decide between using the Entity Framework and LINQ to SQL as an ORM, what's the difference? The way I understand it, the Entity Framework (when used with LINQ to Entities) is a 'big brother' to LINQ to SQL? If this is the case - what advantages does it have? What can it do that LINQ to SQL can't do on its own?

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  • How to assign default values and define unique keys in Entity Framework 4 Designer

    - by csharpnoob
    Hello, I've had a look at the Entity Framework 4. While generating code for the SQL Server 2008 I came to the point where I want to define some default values for some fields. how to define in the designer for a Created DateTime Field the DateTime.Now default value? - Error 54: Default value (DateTime.Now) is not valid for DateTime. The value must be in the form 'yyyy-MM-dd HH:mm:ss.fffZ' how to make for code generation a string Field unique. Like E-Mail or Username can exists only once in the table. I've search alot in the internet and also checked my books Pro Entity Framework 4.0 and Programming Entity Framework. But none of them seems to come up with the default value issue, or using sql commands as default values for database generation. Another thing is, how to prevent on database generation always from droping tables? Instead i want to append non existing fields and keep the data. Thanks for any suggestions.

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  • Entity Framework: Data Centric vs. Object Centric

    - by Eric J.
    I'm having a look at Entity Framework and everything I'm reading takes a data centric approach to explaining EF. By that I mean that the fundamental relationships of the system are first defined in the database and objects are generated that reflect those relationships. Examples Quickstart (Entity Framework) Using Entity Framework entities as business objects? The EF documentation implies that it's not necessary to start from the database layer, e.g. Developers can work with a consistent application object model that can be mapped to various storage schemas When designing a new system (simplified version), I tend to first create a class model, then generate business objects from the model, code business layer stuff that can't be generated, and then worry about persistence (or rather work with a DBA and let him worry about the most efficient persistence strategy). That object centric approach is well supported by ORM technologies such as (n)Hibernate. Is there a reasonable path to an object centric approach with EF? Will I be swimming upstream going that route? Any good starting points?

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  • Selecting Entity Data Model Laguage -- Visual C# source file generated even when i select VB

    - by Nickson
    Am adding an Entity Data Model to an ASP.NET website. When i Add New Item to the website and select ADO.NET Entity Data Model, am asked for the model name and language. I go a head and select Visual Basic as the language, the model is added and the site can compile with out any issues. however, the model it adds a ModelName.Designer.cs source file, instead of a ModelName.Designer.vb source file. am thinking this is strange as its happening with only one of my website. my other sites have .vb designer source file for their Entity Data Models. The site still compiles with out any errors but am afraid some thing is not right. any one experienced this?, is this normal behavior?

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  • EF2: Is there a way to add an Entity to EntityCollection without having to load related Entity?

    - by mutex
    I can set an EntityReference on an entity without having to load the relevent entity as follows: this.CategoryReference.EntityKey = new EntityKey("MyEntities.CategorySet", "Id", 12); So I can set the Category for the entity I'm dealing with to whatever category has id 12 without having to hit the database. But is there a way to do this or something similar on an EntityCollection? So if I now have multiple categories instead of just one, I want to now do something like the following, though it doesn't work: // stand-in category var categoryStandIn = new Category { EntityKey = new EntityKey("MyEntities.CategorySet", "Id", 12) } this.Categories.Add(categoryStandIn);

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  • Entity Framework ObjectContext Life-cycle

    - by Leonardo
    Hello, I'm developing a web application using asp.net 4.0 with Entity Framework. In my apllication I have a page DataEntry.aspx wich has 3 web user control.Each user control manage an entity and use a repository class to access data. The final user before save all the changes can add or remove entity in memory. My question is: how can i share the ObjectContext between the repositories? Basically I need a ObjectContext for the entire session working of DataEntry.aspx. How can I achive this? Thank you

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  • Managing Large Database Entity Models

    - by ChiliYago
    I would like hear how other's are effectively (or not) working with the Visual Studio Entity Designer when many database tables exists. It seems to me that navigating the Designer is tough enough to find what you are looking for with just a few tables but how about a database with say 100 to 200 tables? When a table change is made at the database level how is the model updated? Does it overwrite any manual changes you have made to the model? How would you quickly find an entity in the designer to make a change or inspect a change? Seems unrealistic to be scrolling around looking for specific entity. Thanks for your feedback!

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  • EF 4.x generated entity classes (POCO) and Map files

    - by JBeckton
    I have an MVC 4 app that I am working on and using the code first implementation except I cheated a bit and created my database first then generated my entity classes (poco) from my database using the EF power tools (reverse engineer). I guess you can say I did database first method but I have no edmx file just the context class and my entity classes (poco) I have a few projects in the works using MVC and EF with pocos but just the one project I used the tool to generate my pocos from the database. My question is about the mapping files that get created when I generate my pocos using the tool. What is the purpose of these Map files? I figured the map files are needed when generating the db from the model like with the true code first method, in my case where I am using a tool to generate my model from the database do the map files have any influence on how my app uses the entity classes?

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