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  • Do entity collections and object sets implement IQueryable<T>?

    - by Chevex
    I am using Entity Framework for the first time and noticed that the entities object returns entity collections. DBEntities db = new DBEntities(); db.Users; //Users is an ObjectSet<User> User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? user.Posts; //Posts is an EntityCollection<Post> Post post = user.Posts.Where(x => x.PostID == "123").First(); //Is this getting executed in the SQL or in memory? Do both ObjectSet and EntityCollection implement IQueryable? I am hoping they do so that I know the queries are getting executed at the data source and not in memory. EDIT: So apparently EntityCollection does not while ObjectSet does. Does that mean I would be better off using this code? DBEntities db = new DBEntities(); User user = db.Users.Where(x => x.Username == "test").First(); //Is this getting executed in the SQL or in memory? Post post = db.Posts.Where(x => (x.PostID == "123")&&(x.Username == user.Username)).First(); // Querying the object set instead of the entity collection. Also, what is the difference between ObjectSet and EntityCollection? Shouldn't they be the same? Thanks in advance!

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  • Core data many-to-many relationship - Predicate question

    - by Garry
    In my Core Data model I have two entities: List and Patient. List has an attribute called 'name'. A List can have any number of Patients and each Patient can belong to any number of different lists. I have therefore set a relationship on List called 'patients' that has an inverse to-many relationship to Patient AND a relationship on Patient called 'lists' that has a to-many relationship to List. What I'm struggling to figure out is how to create a Predicate that will select all Patients that belong to a particular List name. How would I go about this? I have never used relationships before in Core Data. Thanks,

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  • SQLAlchemy - relationship limited on more than just the foreign key

    - by Marian
    I have a wiki db layout with Page and Revisions. Each Revision has a page_id referencing the Page, a page relationship to the referenced page; each Page has a all_revisions relationship to all its revisions. So far so common. But I want to implement different epochs for the pages: If a page was deleted and is recreated, the new revisions have a new epoch. To help find the correct revisions, each page has a current_epoch field. Now I want to provide a revisions relation on the page that only contains its revisions, but only those where the epochs match. This is what I've tried: revisions = relationship('Revision', primaryjoin = and_( 'Page.id == Revision.page_id', 'Page.current_epoch == Revision.epoch', ), foreign_keys=['Page.id', 'Page.current_epoch'] ) Full code (you may run that as it is) However this always raises ArgumentError: Could not determine relationship direction for primaryjoin condition ...`, I've tried all I had come to mind, it didn't work. What am I doing wrong? Is this a bad approach for doing this, how could it be done other than with a relationship?

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  • How to reduce Entity Framework 4 query compile time?

    - by Rup
    Summary: We're having problems with EF4 query compilation times of 12+ seconds. Cached queries will only get us so far; are there any ways we can actually reduce the compilation time? Is there anything we might be doing wrong we can look for? Thanks! We have an EF4 model which is exposed over the WCF services. For each of our entity types we expose a method to fetch and return the whole entity for display / edit including a number of referenced child objects. For one particular entity we have to .Include() 31 tables / sub-tables to return all relevant data. Unfortunately this makes the EF query compilation prohibitively slow: it takes 12-15 seconds to compile and builds a 7,800-line, 300K query. This is the back-end of a web UI which will need to be snappier than that. Is there anything we can do to improve this? We can CompiledQuery.Compile this - that doesn't do any work until first use and so helps the second and subsequent executions but our customer is nervous that the first usage shouldn't be slow either. Similarly if the IIS app pool hosting the web service gets recycled we'll lose the cached plan, although we can increase lifetimes to minimise this. Also I can't see a way to precompile this ahead of time and / or to serialise out the EF compiled query cache (short of reflection tricks). The CompiledQuery object only contains a GUID reference into the cache so it's the cache we really care about. (Writing this out it occurs to me I can kick off something in the background from app_startup to execute all queries to get them compiled - is that safe?) However even if we do solve that problem, we build up our search queries dynamically with LINQ-to-Entities clauses based on which parameters we're searching on: I don't think the SQL generator does a good enough job that we can move all that logic into the SQL layer so I don't think we can pre-compile our search queries. This is less serious because the search data results use fewer tables and so it's only 3-4 seconds compile not 12-15 but the customer thinks that still won't really be acceptable to end-users. So we really need to reduce the query compilation time somehow. Any ideas? Profiling points to ELinqQueryState.GetExecutionPlan as the place to start and I have attempted to step into that but without the real .NET 4 source available I couldn't get very far, and the source generated by Reflector won't let me step into some functions or set breakpoints in them. The project was upgraded from .NET 3.5 so I have tried regenerating the EDMX from scratch in EF4 in case there was something wrong with it but that didn't help. I have tried the EFProf utility advertised here but it doesn't look like it would help with this. My large query crashes its data collector anyway. I have run the generated query through SQL performance tuning and it already has 100% index usage. I can't see anything wrong with the database that would cause the query generator problems. Is there something O(n^2) in the execution plan compiler - is breaking this down into blocks of separate data loads rather than all 32 tables at once likely to help? Setting EF to lazy-load didn't help. I've bought the pre-release O'Reilly Julie Lerman EF4 book but I can't find anything in there to help beyond 'compile your queries'. I don't understand why it's taking 12-15 seconds to generate a single select across 32 tables so I'm optimistic there's some scope for improvement! Thanks for any suggestions! We're running against SQL Server 2008 in case that matters and XP / 7 / server 2008 R2 using RTM VS2010.

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  • EntityFramework .net 4 Update entity with a simple method

    - by Dennis Larsen
    I was looking at this SO question: http://stackoverflow.com/questions/1168215/ado-net-entity-framework-update-only-certian-properties-on-a-detached-entity. This was a big help for me. I know now that I need to attach an entity before making my changes to it. But how can do I do this: I have an MVC website, a Customer Update Page with fields: ID, Name, Address, etc. My MVC is parsing this into a Customer entity. How do I do the following: Update my entity and Save the changes to it. Catch the exception if my changes have been made since I loaded my entity.

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  • Entity update from ASP.NET MVC page with post to Edit action

    - by mare
    I have a form that posts back to /Edit/ and my action in controller looks like this: // // POST: /Client/Edit [AcceptVerbs(HttpVerbs.Post)] public ActionResult Edit(Client client) My form includes a subset of Client entity properties and I also include a hidden field that holds an ID of the client. The client entity itself is provided via the GET Edit action. Now I want to do entity update but so far I've only been trying without first loading the entity from the DB. Because the client object that comes in POST Edit has everything it needs. I want to update just those properties on the entity in datastore. So far I've tried with Context.Refresh() and AttachTo() but with no success - I'm getting all sorts of exceptions. I inspected the entity object as it comes from the web form and it looks fine (it does have an ID and entered data) mapped just fine. If I do it with Context.SaveChanges() then it just inserts new row..

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  • Core Data migration of to-one relationship to to-many relationship

    - by westsider
    I have a deployed app that samples measurements from sensors (e.g., Temp °C, Pressure kPa). The user can create Experiments and collect samples. Each sample is stored as a Run, such that there is a one-to-many relationship from Experiment to Run. In the interest of performance, Run has a to-one relationship with Data entity (which is where the actual raw data is stored); this allows some Run attributes to be loaded without necessarily loading lots of data. Most of our sensors have multiple measurements, so it would be nice to store all the data that is actually being sampled. But this means that the Run <--- Data relationship needs to become Run <-- Data (to use Xcode's convention). I am faced with trying to migrate data from old Run to-one Data model to new Run to-many Data model. Can this be done using Mapping Models? If so, does anyone have any pointers to examples? If not, does anyone have any pointers to examples of how to do that? Thanks for any pointers or advice.

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  • Entity Framework 4 and SQL Compact 4: How to generate database?

    - by David Veeneman
    I am developing an app with Entity Framework 4 and SQL Compact 4, using a Model First approach. I have created my EDM, and now I want to generate a SQL Compact 4.0 database to act as a data store for the model. I bring up the Generate Database Wizard and click the New Connection button to create a connection for the generated file. The Choose Data Source dialog appears, but SQL Compact 4.0 is not listed in the list of available data sources: I am running VS 2010 SP1 (beta) and I have installed the VS 2010 Tools for SQL Compact 4.0. I can create a SQL Compact 4.0 data connection from the Server Explorer. It is only in the Generate Database Wizard that the 4.0 option doesn't appear. BTW, my SQL Compact 4.0 installation does include System.Data.SqlServerCe.Entity.dll. So I should have the SQL Compact components I need. Am I doing something incorrectly, or is this a bug? Does anyone have a fix or a workaround? Thanks for your help.

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  • In an Entity-Component-System Engine, How do I deal with groups of dependent entities?

    - by John Daniels
    After going over a few game design patterns, I have settle with Entity-Component-System (ES System) for my game engine. I've reading articles (mainly T=Machine) and review some source code and I think I got enough to get started. There is just one basic idea I am struggling with. How do I deal with groups of entities that are dependent on each other? Let me use an example: Assume I am making a standard overhead shooter (think Jamestown) and I want to construct a "boss entity" with multiple distinct but connected parts. The break down might look like something like this: Ship body: Movement, Rendering Cannon: Position (locked relative to the Ship body), Tracking\Fire at hero, Taking Damage until disabled Core: Position (locked relative to the Ship body), Tracking\Fire at hero, Taking Damage until disabled, Disabling (er...destroying) all other entities in the ship group My goal would be something that would be identified (and manipulated) as a distinct game element without having to rewrite subsystem form the ground up every time I want to build a new aggregate Element. How do I implement this kind of design in ES System? Do I implement some kind of parent-child entity relationship (entities can have children)? This seems to contradict the methodology that Entities are just empty container and makes it feel more OOP. Do I implement them as separate entities, with some kind of connecting Component (BossComponent) and related system (BossSubSystem)? I can't help but think that this will be hard to implement since how components communicate seem to be a big bear trap. Do I implement them as one Entity, with a collection of components (ShipComponent, CannonComponents, CoreComponent)? This one seems to veer way of the ES System intent (components here seem too much like heavy weight entities), but I'm know to this so I figured I would put that out there. Do I implement them as something else I have mentioned? I know that this can be implemented very easily in OOP, but my choosing ES over OOP is one that I will stick with. If I need to break with pure ES theory to implement this design I will (not like I haven't had to compromise pure design before), but I would prefer to do that for performance reason rather than start with bad design. For extra credit, think of the same design but, each of the "boss entities" were actually connected to a larger "BigBoss entity" made of a main body, main core and 3 "Boss Entities". This would let me see a solution for at least 3 dimensions (grandparent-parent-child)...which should be more than enough for me. Links to articles or example code would be appreciated. Thanks for your time.

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  • Complex Entity Framework linked-graphs issue: how to limit change set / break the graph?

    - by Hightechrider
    I have an EDMX containing Sentences, and Words, say and a Sentence contains three Words, say. Appropriate FK relationships exist between the tables. I create some words: Word word1 = new Word(); Word word2 = ... I build a Sentence: Sentence x = new Sentence (word1, word2, word3); I build another Sentence: Sentence y = new Sentence (word1, word4, word5); I try to save x to the database, but EF builds a change set that includes everything, including y, word4 and word5 that aren't ready to save to the database. When SaveChanges() happens it throws an exception: Unable to determine the principal end of the ... relationship. Multiple added entities may have the same primary key. I think it does this because Word has an EntityCollection<Sentence> on it from the FK relationship between the two tables, and thus Sentence y is inextricably linked to Sentence x through word1. So I remove the Navigation Property Sentences from Word and try again. It still tries to put the entire graph into the change set. What suggestions do the Entity Framework experts have for ways to break this connection. Essentially what I want is a one-way mapping from Sentence to Word; I don't want an EntityCollection<Sentence> on Word and I don't want the object graph to get intertwined like this. Code sample: This puts two sentences into the database because Verb1 links them and EF explores the entire graph of existing objects and added objects when you do Add/SaveChanges. Word subject1 = new Word(){ Text = "Subject1"}; Word subject2 = new Word(){ Text = "Subject2"}; Word verb1 = new Word(){ Text = "Verb11"}; Word object1 = new Word(){ Text = "Object1"}; Word object2 = new Word(){ Text = "Object2"}; Sentence s1 = new Sentence(){Subject = subject1, Verb=verb1, Object=object1}; Sentence s2 = new Sentence(){Subject=subject2, Verb=verb1, Object=object2}; context.AddToSentences(s1); context.SaveChanges(); foreach (var s in context.Sentences) { Console.WriteLine(s.Subject + " " + s.Verb + " " + s.Object); }

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  • Mapping composite foreign keys in a many-many relationship, with overlapping components.

    - by Kirk Broadhurst
    I have a Page table and a View table. There is a many-many relationship between these two via a PageView table. Unfortunately all of these tables need to have composite keys (for business reasons). Page has a primary key of (PageCode, Version), View has a primary key of (ViewCode, Version). PageView obviously enough has PageCode, ViewCode, and Version. The FK to Page is (PageCode, Version) and the FK to View is (ViewCode, Version) Makes sense and works, but when I try to map this in Entity framework I get Error 3021: Problem in mapping fragments...: Each of the following columns in table PageView is mapped to multiple conceptual side properties: PageView.Version is mapped to (PageView_Association.View.Version, PageView_Association.Page.Version) So clearly enough, EF is having a complain about the Version column being a common component of the two foreign keys. Obviously I could create a PageVersion and ViewVersion column in the join table, but that kind of defeats the point of the constraint, i.e. the Page and View must have the same Version value. Has anyone encountered this, and is there anything I can do get around it? Thanks!

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  • Laravel 4 showing all field from one to one relationship in

    - by rivai04
    I'm trying to show all field of the chosen row from one to one relationship... Route Route::get('relasi-pasien', function() { $pasien = PasienIri::where('no_ipd', '=', '100')->first(); foreach($pasien->keadaanumum as $temp) { echo'<li> Name : '.$temp->name. 'Tekdar: '.$temp->tekdar. 'Nadi : '.$temp->nadi. '</li>'; } }); Relation at PasienIri's model public function keadaanumum() { return $this->hasOne('KeadaanUmum', 'no_ipd'); } Relation at KeadaanUmum's Model public function pasieniri() { return $this->belongsTo('PasienIri', 'no_ipd'); } When I used that way, it showed error: 'Trying to get property of non-object' But if I just trying to show only one of the field, it works, showing one field: Route::get('relasi-pasien', function() { $pasien = PasienIri::where('no_ipd', '=', '100')->first(); return $pasien->keadaanumum->name; }); anyone could help me to show all field with one to one relationship or I really have to change it to one to many relationship? cause if I change it to one to many relationship, it works

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  • Is Moving Entity Framework objects over a webservice really the best way?

    - by aceinthehole
    I've inherited a .NET project that has close to 2 thousand clients out in the field that need to push data periodically up to a central repository. The clients wake up and attempt to push the data up via a series of WCF webservices where they are passing each entity framework entity as parameter. Once the service receives this object, it preforms some business logic on the data, and then turns around and sticks it in it's own database that mirrors the database on the client machines. The trick is, is that this data is being transmitted over a metered connection, which is very expensive. So optimizing the data is a serious priority. Now, we are using a custom encoder that compresses the data (and decompresses it on the other end) while it is being transmitted, and this is reducing the data footprint. However, the amount of data that the clients are using, seem ridiculously large, given the amount of information that is actually being transmitted. It seems me that entity framework itself may be to blame. I'm suspecting that the objects are very large when serialized to be sent over wire, with a lot context information and who knows what else, when what we really need is just the 'new' inserts. Is using the entity framework and WCF services as we have done so far the correct way, architecturally, of approaching this n-tiered, asynchronous, push only problem? Or is there a different approach, that could optimize the data use?

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  • Dump Linq-To-Sql now that Entity Framework 4.0 has been released?

    - by DanM
    The relative simplicity of Linq-To-Sql as well as all the criticism leveled at version 1 of Entity Framework (especially, the vote of no confidence) convinced me to go with Linq-To-Sql "for the time being". Now that EF 4.0 is out, I wonder if it's time to start migrating over to it. Questions: What are the pros and cons of EF 4.0 relative to Linq-To-Sql? Is EF 4.0 finally ready for prime time? Is now the time to switch over?

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  • Flexible design - customizable entity model, UI and workflow

    - by Ngm
    Hi All, I want to achieve the following aspects in the software I am building: 1. Customizable entity model 2. Customizable UI 3. Customizable workflow I have thought about an approach to achieve this, I want you to review this and make suggestions: Entity objects should be plain objects and will hold just data Separate Entity model and DB Schema by using an framework (like NHibernate?). This will allow easy modification of entity objects. Business logic to fetch/modify entities has to be granular enough so that they can be invoked as part of the workflow. Business objects should not hold any state, and hence will contain only static methods The workflow will decide depending upon the "state" of an entity/entities which methods on business object/objects to invoke. The workflow should obtain the results of the processing and then pass on the business objects to the appropriate UI screen. The UI screen has to contain instructions about how to display a given entity/entites. Possibly the UI has to be generated dynamically based on a set of UI instructions. (like XUL) What do you think about this approach? Suggest which existing frameworks (like NHiberante, Window Workflow) fit into this model, so that I will not spend time on coding these frameworks Also suggest is there any asp.net framework that can generate dynamic asp.net ajax pages based on a set of UI instructions (like Mozilla XUL)? I have recently been exploring Apache Ofbiz and was impressed by its ability to customize most areas of the application: UI, workflow, entities. Is there any similar (not necessarily an ERP system) application developed in C#/.Net which offers a similar level of customization? I am looking for examples of applications developed in C# that are highly customizable in terms of UI, Workflow and Entity Model

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  • Does Entity Framework 4 not support property automatic lazy loading for model-first entities?

    - by KallDrexx
    All references that I find for lazy loading say it's possible but they all mention POCOs and that's it. I am using EF4 with the model-first methodology. In my model diagram I have a Project table and a UserObject table, with a 1 to many relationship between them. However, in code, when I have a valid UserObject and I attempt to get the project performing: Project prj = userobj.Project. Unfortunately, this doesn't work as it claims that UserObject.Project is null. It seems like I have to explicitly load the Project object via calling UserObject.ProjectReference.Load() prior to calling .Project. Is there any way for this to occur automatically when I access the .Project property?

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  • What the best way to wire up Entity Framework database context (model) to ViewModel in MVVM WPF?

    - by hal9k2
    As in the question above: What the best way to wire up Entity Framework database model (context) to viewModel in MVVM (WPF)? I am learning MVVM pattern in WPF, alot of examples shows how to implement model to viewModel, but models in that examples are just simple classes, I want to use MVVM together with entity framework model (base first approach). Whats the best way to wire model to viewModel. Thanks for answers. //ctor of ViewModel public ViewModel() { db = new PackageShipmentDBEntities(); // Entity Framework generated class ListaZBazy = new ObservableCollection<Pack>(db.Packs.Where(w => w.IsSent == false)); } This is my usual ctor of ViewModel, think there is a better way, I was reading about repository pattern, not sure if I can adapt this to WPF MVVM

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  • 2-Way databinding with Entity Framework and WPF DataGrid

    - by Mike Gates
    I'm having trouble adding an Entity Framework entity to a ObjectContext's EntitySet automatically using the WPF 4.0 DataGrid's add functionality. Here's the setup: DataGrid--BoundTo--ListCollectionView--BoundTo--EntitySet When I interactively add a row to the DataGrid, the EntitySet does not have a new entity added to it. Updating the row's cell data does in fact update the bound entity's properties, however. Any idea what I could be doing wrong?

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  • Entity Framework 4 - Delay Loading Expensive Fields

    - by JohnnyO
    I know this same question was asked for Entity Framework 1, but now that Entity Framework 4 has come out, and Microsoft claims that it provides all of the features of Linq to Sql + more, does Entity Framework now support lazy loading expensive properties? In Linq to Sql, this is extremely easy. There's a Delay Loaded option on any property (accessible through the Designer) that can simply be toggled on or off. Is there something similar in Entity Framework? Thanks

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  • How to model my database when using entity framework 4?

    - by Junior Ewing
    Trying to wrap my head around the best approach in modelling a database when we are using Entity Framework 4 as the ORM layer. We are going to use asp.net mvc 2 for the application. Is it worth trying to model using the class diagram modeller that comes with Visual Studio 2010 where you graphically configure your models into the EDMX file and then generate out the database structure? I have run into a bunch of non trivial issues and for complex many to many mappings or multi primary key entities the answer is not that obvious even after poking around a while with the tools. I figure its easy at this point to give up and start modelling the DB using real, working DB modelling tools and then try to generate out the EDMX from the database, rather than trying to do the model first approach.

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  • Entity Framework 4 - Handling very large (1000+ tables) data models?

    - by David Kreps
    We've got a database with over 1000+ tables and would like to consider using EF4 for our data access layer, but I'm concerned about the practical realities of using it for such a large data model. I've seen this question and read about the suggested solutions here and here. These may work, but appear to refer to the first version of the Entity Framework (and are more complex than I'd like). Does anyone know if these solutions have been improved upon in EF4? Or have other suggestions all together? Thanks.

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  • Obstacle Avoidance steering behavior: how can an entity avoid an obstacle while other forces are acting on the entity?

    - by Prog
    I'm trying to implement the Obstacle Avoidance steering behavior in my 2D game. Currently my approach is to apply a force on the entity, in the direction of the normal of the heading, scaled by a number that gets bigger the closer we are to the obstacle. This is supposed to push the entity to the side and avoid the obstacle that blocks it's way. However, in the same time that my entity tries to avoid an obstacle, it Seeks to a point more or less behind the obstacle (which is the reason it needs to avoid the obstacle in the first place). The Seek algorithm constantly applies a force on the entity that pushes it (more or less) in the direction of the obstacle, while the Obstacle Avoidance algorithm constantly applies a force that pushes the entity away (more accurately, to the side) of the obstacle. The result is that sometimes the entity succesfully avoids the obstacle, and sometimes it collides with it, depending on the strength of the avoidance force I'm applying. How can I make sure that a force will succeed in steering the entity in some direction, while other forces are currently acting on the entity? (And while still looking natural). I can't allow entities to collide with obstacles when realistically they should be able to easily avoid them, doesn't matter what they're currently doing. Also, the Obstacle Avoidance algorithm is made exactly for the case where another force is acting on the entity. Otherwise it wouldn't be moving and there would be no need to avoid anything. So maybe I'm missing something. Thanks

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  • 2-Way databinding with Entity Framework and WPF DataGrid , is Possible ?

    - by Panindra
    i am working on POS application using SQL CE , WPF , Entity framework 3.5sp2 and iam trying to use data grid as my Order Entry Control for User to enter Products Order . Iam plannning to bind this to enitiy frmae work model , abd looking for 2 way updating ? private void button1_Click(object sender, RoutedEventArgs e) { using (MasterEntities nwEntities = new MasterEntities()) { var users = from d in nwEntities.Companies select new { d.CompanyId, d.CompanyName, d.Place }; listBox1.DataContext = users; dataGrid1.DataContext = users; // foreach (String c in customers) // { // MessageBox.Show(c.ToString()); // } } } When try to double clikc on the datagrid it through s a error with Caption " Invalid Operation Execption was unhandled " and Message " A TwoWay or OneWayToSource binding cannot work on the read-only property 'CompanyId' of type '<f__AnonymousType0`3[System.Int32,System.String,System.String]'. whats wrong here and my xaml coding goes like this <Grid> <ListBox Name="listBox1" ItemsSource="{Binding}" /> <Button Content="Show " Name="button1" Click="button1_Click" /> <DataGrid AutoGenerateColumns="False" Name="dataGrid1" ItemsSource="{Binding}" > <DataGrid.Columns> <DataGridTextColumn Header=" ID" Binding="{Binding CompanyId}"/> <DataGridTextColumn Header="Company Name" Binding="{Binding CompanyName}"/> <DataGridTextColumn Header="Place" Binding="{Binding Place}" /> </DataGrid.Columns> </DataGrid> </Grid> EDITED : i made the changes shown by @vorrtex, But, then i added another button to save the chages and in button click event i added follwing code , butit showing Updating error private void button2_Click(object sender, RoutedEventArgs e) { nwEntities.SaveChanges(); }

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