entity-framework

Using T4 templates to add custom code to EF4 generated entities?

I am getting started with Entity Framework 4, using model-first development. I am building a simple WPF demo app to learn the framework. My app has two entities, Topic and Note. A Topic is a discussion topic; it has Title, Text, and DateRevised properties. Topic also has a Notes collection property. a Note has DateCreated and Text proper...

Entity Framework UpdateException relationships in Added and Deleted states

Hi, I have a table of Plants and Information. Plants have an ID, Name, ..., MainInformationID Information have an ID, Title, ..., PlantID One plant can have many information, but only one MainInformation. Information can only have one plant. I have a class ViewModel which contains observable collections of plants and information whi...

How to delete an object by id with entity framework

It seems to me that I have to retrieve an object before I delete it with entity framework like below var customer = context.Customers.First(c => c.Id = 1); context.DeleteObject(customer); context.Savechanges(); So I need to hit database twice. Is there a easier way? Thanks ...

can entity framework combine sql command in a batch

I write the following code with entity framework context.AddObject(obj1); context.AddObject(obj2); context.DeleteObject(obj3); context.SaveChanges(); The last command issue multiple sql command in separate branches, it seems to be is not efficient at all, is there a option to send all command in a single batch? Thanks ...

How can I share an entity framework model across website users

Hello, Currently my website is based around MVC and the Entity Framework running against a SQL Server 2005 database. So far, it has all been running very smoothly, and I really enjoy MVC and its slimmer more concise code (and no huge viewstates or soul destroying postbacks ;)) Recently I was working on upgrading the site to use a simpl...

How to override Equals on a object created by an Entity Data Model?

I have an Entity Data Model that I have created, and its pulling in records from a SQLite DB. One of the Tables is People, I want to override the person.Equals() method but I'm unsure where to go to make such a change since the Person object is auto-generated and I don't even see where that autogen code resides. I know how to override Eq...

Creating blob properties with Entity Framework 4?

I am creating an EF4 model-first application with a WPF UI. One of the controls on my UI is a RichTextDocument, which outputs a WPF FlowDocument. I can either serialize the FlowDocument to a byte array, or extract its XAML markup as a string. I would prefer to use binary serialization, if I can. Here are my questions: If I serialize t...

The underlying provider failed on Open

I was using .mdf for connect to DB and entityClient. Now i want to change connection string that trehe will be no .mdf Is this conectionstring correct <connectionStrings> <!--<add name="conString" connectionString="metadata=res://*/conString.csdl|res://*/conString.ssdl|res://*/conString.msl;provider=System.Data.SqlClient;provider conne...

Create a many to many relationship in Entity Framework skipping extra data in the link table.

I would like to model the following many to many relationship. Table A ID Field1 Field2 Table B ID Field1 Field2 LinkTable A_ID B_ID Field_I_want_to_ignore As I understand it, if LinkTable.Field_I_want_to_ignore was not present, the Entity Model Designer would automatically create a Many to Many relationship between entity A and ent...

Problem with cascade delete using Entity Framework and System.Data.SQLite

I have a SQLite DB that is set up so when I delete a Person the delete is cascaded. This works fine when I manually delete a Person (all records that reference the PersonID are deleted). But when I use Entity Framework to delete the Person I get an error: System.InvalidOperationException: The operation failed: The relationship could no...

Entity Framework 4 / POCO - Where to start?

Hi, I've been programming for a while and have used LINQ-To-SQL and LINQ-To-Entities before (although when using entities it has been on a Entity/Table 1-1 relationship - ie not much different than L2SQL) I've been doing a lot of reading about Inversion of Control, Unit of Work, POCO and repository patterns and would like to use this m...

error with linq join

I have this linq query: var segreterie = from s in db.USR_Utenti join h in db.USR_Accounts on new {s.ID, settings.GruppoSegreteria} equals new {h.USR_UtentiReference,h.ID_Gruppo} select s; that has this problem: The type of one of the expressions in the join clause is incorrect. Type infere...

entity framework, loadproperty not working - The selector expression for LoadProperty must be a MemberAccess for the property.

The selector expression for LoadProperty must be a MemberAccess for the property. I'm converting some C# to VB, this is the C# line: entities.LoadProperty((MyType)MyTargetObject, c => c.MyProperty); I convert it to VB like so: entities.LoadProperty(DirectCast(MyTargetObject, MyType), Function(c) c.MyProperty) However I get the err...

EDM -> POCO -> WCF (.NET4) But transferring Collections causes IsReadOnly set to TRUE

Ok, this may sound a little 'unorthodox', but...using VS2010 and the new POCO t4 template for Entity Framework (http://tinyurl.com/y8wnkt2), I can generate nice POCO's. I can then use these POCO's (as DTO's) in a WCF service essentially going from EDM all the way through to the client. Kinda what this guys is doing (http://tinyurl.com/yb...

ObjectContext.SaveChanges() fails with SQL CE

I am creating a model-first Entity Framework 4 app that uses SQL CE as its data store. All is well until I call ObjectContext.SaveChanges() to save changes to the entities in the model. At that point, SaveChanges() throws a System.Data.UpdateException, with an inner exception message that reads as follows: Server-generated keys and serv...

Generating Entity Keys

I have run into my first dissapointment with Entity Framework 4. It turns out that SQL CE, when used with EF4, does not support autogenerated primary keys. I get a System.Data.UpdateException from OnjectContext.SaveChanges() with this message: Server-generated keys and server-generated values are not supported by SQL Server Compact. So...

Can I Use EF Across Multiple DBs in One SQLServer Instance?

Hello, I have been searching the blogs and articles but I have not found much support for this scenario. I have been poking around EF and realized that I could create views that contained data from multiple databases and then build the EF object model off of those views. Although it works I am not sure about the usual issues of performa...

View SQL generated by SaveChanges in EF

Is there a simple way to view the machine generated SQL for SaveChanges() on an Entity Framework context? ...

EF problem with entity re-ordering and uniqueness constraint

I am using Entity Framework and I've come to an interesting stumbling block. Let's say there is a db table "Item" with "sequence" column of type int (and others of course). Column "sequence" must be unique and it is used for (re)ordering of items. EF maps this table to "Item" class with "sequence" int property. Now let's say I want to s...

GUID or int entity key with SQL Compact/EF4?

This is a follow-up to an earlier question I posted on EF4 entity keys with SQL Compact. SQL Compact doesn't allow server-generated identity keys, so I am left with creating my own keys as objects are added to the ObjectContext. My first choice would be an integer key, and the previous answer linked to a blog post that shows an extension...