Entity Framework Getting Objects Not Immediately Related?
Jun 24, 2010
I am using Entity Framework for my .NET application. I have been able to return objects and their directly-related objects as well (very convenient), but I am having trouble getting the objects of those objects.
IEnumerable<Lot> i = (((ObjectSet<Car>)_carRepository.GetQuery()) .Include(a => a.CarTypes).Take(10).ToList()
This works and I can access carTypes, however I cannot figure out how to access tables associated with CarTypes (e.g. tables which have fields associated with the car types). I tried to use a Join however I was unable to figure out how to get it to work right.
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Similar Messages:
Aug 5, 2010
I am trying to add a new entity and have to refernce associated data to add it. I cannot load the Referencetables. Giving "The EntityReference could not be loaded because it is not attached to an ObjectContext." How do i complete this task in Entity Framework 3.5
[Code]....
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Mar 19, 2010
I have the following tables:
Campaigns (CampaignId, CampaignName, etc)
Urls(UrlId, CampaignId, UrlText)
I have a relationship setup between Campaigns table and Urls (FK_Url_Campaign) everything works fine when I try to add a new campaign but when I try to insert a new Url I get:
Entities in 'DatabaseEntity.Url' participate in the 'FK_Url_Campaign' relationship. 0 related 'Campaign' were found. 1 'Campaign' is expected.
This is my code:
// INSERT
public int Insert()
{
Url dbUrl = new Url();
dbUrl.CampaignId = (int)CampaignId;
dbUrl.Url1 = (string)Url;
context.AddToUrl(dbUrl);
context.SaveChanges();
return (int)dbUrl.UrlId;
}
Pretty much i want update/add new campaign and then I call Insert for Url. how would i go about doing this?
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Sep 9, 2010
I use VS 2010 Ultimate. I created an 'asp.net web application' from scratch, added a 'ADO.NET Entity Model' to my project (EF4).
The problem I'm having is that whenever I try and use an EntityDataSource to pull data out of my entity model I am near constantly getting the following error:
"The metadata specified in the connection string could not be loaded. Consider rebuilding the web project to build assemblies that may contain metadata. The following error(s) occurred:"
[code]....
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Dec 6, 2010
I've been tasked to convert our old DAL that have gen objects to possibly the Entity Framework 4.0. We create objects inheriting from our genned objects and have a ton methods our legacy codes uses. Does anyone have an idea or possible solution on how to create an entity framework model that maps to our old genned objects? Or a solution that requires us to modify our legacy code minimally?
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Oct 12, 2010
I have a gridview displaying "registrationtype id" (FK) from the registration table. I want it to display the related name instead of the id from the registartiontype table.
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Jun 11, 2010
I'm trying to use formview in order to do insert of a new entity object (called Customer) Customer has a reference to another entity called Address. How can I fill both of them in the same formview?
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Feb 20, 2011
I want to be able to update a model and all its collections of child objects in the same view. I have been referred to these examples: http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx and http://blog.stevensanderson.com/2010/01/28/editing-a-variable-length-list-aspnet-mvc-2-style/ .
For example, I have an object Consultant, that has a collection of "WorkExperiences". All this is in an Entity Framework model. In the view, the simple properties of the Consultant object is no problem, but the collection I cannot get a textbox to show up for. I tried following the examples in the links above, but it doesn't work. The problem is, in those examples the model is just a list (not an object with a child list property). And also, the model again is an EF model. And for some reason that doesn't seem to work as in those examples.
[Code]....
This stuff with the EditorTemplate works fine in Phil Haack's sample project, which I downloaded to try, but here, with the EF model or whatever the problem is, I don't get any textbox at all. The table in the view is just there as a test, because in the table I do get the rows for WorkExperiences, whether I add an empty WorkExperience object or fill out its properties doesn't matter, the rows show up for each object. But again, no textbox...
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Apr 22, 2010
I have a question, much liket this unanswered one. I'm trying to work with the entity framework, and having a tough time getting my foreign tables to update. I have something basically like this in the DB:
Incident (table):
-ID
-other fields
Responses (table):
-FK:Incident.ID
-other fields
And and entities that match:
Incident (entity)
-ID
-Other fields
-Responses (EntityCollection of Responses via navigation property)
Each Incident can have 0 or more responses.
In my Webpage, I have a form to allow the user to enter all the details of an Incident, including a list of responses. I can add everything to the database when a new Incident is created, however I'm having difficulty with editing the Incident.
When the page loads for edit, I populate the form and then store the responses in the viewstate. When the user changes the list of responses (adds one, deletes one or edits one). I store this back into the viewstate. Then when the user clicks the save button, I'd like to save the changes to the Incident and the Responses back to the DB. I cannot figure out how to get the responses from the detached viewstate into the Incident object so that they can be updated together.
Currently when the user clicks save, I'm getting the Incident to edit from the db, making changes to the Incident's fields and then saving it back to the DB. However I can't figure out how to have the detached list of responses from the viewstate attach to the Incident. I have tried the following without success:
Clearning the Incident.Responses collection and adding the ones from the viewstate back in:
Incident.Responses.Clear()
for each objResponse in Viewstate("Responses")
Incident.Responses.add(objResponse)
next
Creating an EntityCollection from my list and then assiging that to the Incident.Responses
Incident.Responses = EntityCollectionFromViewstateList
Iterating through the responses in Incident.Response and assigning the corresponding object from viewstate:
for each ObjResponse in Incident.Responses
objResponse = objCorrespondingModifedResonseFromViewState
Next
These all fail, I'd like to be able to merge the changes into the Inicdent object so that when the BLL calls SaveChanges on the changes to both the Incident and Responses will happen at the same time.
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Apr 2, 2010
I have a table in my database with a one to many relationship to another table, which has a relationship to a third table:
[Code].....
This seems to work fine. My question to you good folks: Is there a correct way to do this? I tried following the making a custom model binder per the blog link I posted above but it didn't work (there was an issue with reflection, the code expected certain properties to exist) and I needed to get something going ASAP. PS - I tried to cleanup the code to hide specific information, so beware I may have hosed something up.
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Nov 5, 2010
i create example using Northwind database so i create a new website and add new ADO.Net Entity Data Model (.edmx) called Northwind.edmx and i add Categories and Products table inside this (.edmx) file
and add new ADO.Net Data Servuce called "ADODataService" and add it as WebReferences called NorthwindService
so i add new web page and drag DropdownList and Gridview as i want to bind Dropdownlist to all categories and when i select category from Dropdownlist bind Gridview to all Products related to this category
so my code
[Code]....
and my code
[Code]....
so when i select category from Dropdownlist nothing happen :(
also you will find commented code in method BindCategory whuch is not work also.
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Oct 25, 2010
Is there a way to export a EF 4.0 Data Model to EF 3.5?
I looked around and found that we are not able to access EF 4.0 from a ASP.Net 3.5 project here: [URL]
Our project is the 1st to go to .Net 4.0 using Entity Framework and we (the team) were wondering if there was a way for the other projects that "might" need to access our data that are still using the .Net 3.5 framework.
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Sep 29, 2010
getting data from multiple Entities models into an MVC controller. Most of the examples I have seen for using EF in an MVC2 app only use a single entitiy.
I have just started using MVC2 in C# using the Entity Framework models (CIOps.model) created from an SQL database. I can create the controller and views using single tables of the model in MVC2, but I just cannot get my head around how to get data from multiple entity tables into the controller (similar to joins in T-SQL). I have included an example below of the controller code that works with a single entity table, tbl_tours (tbl_tour in DB).
Could someone please illustrate how this code would be changed to include additional columns from FK tables in addition to tbl_tours columns. E.g. the clients name from the tbl_clients, the coordinators name from the tbl_employees, and costs from tbl_costs entities? Is it possible to do this directly using the EF model entities/classes that are already created and not use LINQ, POCO, Repositories, etc.? The FK relationships are already in the EF models. I have included the whole controller code, but I just need a few examples of how to join the multiple entities, not rewrite every CRUD function function in the controller. I think this will get me over the hump in using EF in an MVC2 App. Also ignore the fact I am using the home controller, this will change in the application.
[Code]....
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May 29, 2010
I have and Article object that I update in my controller.... the object is passed into the controller and then I just call UpdateModel(inArticle) and it was all good. I now expanded my article to belong to a category and want to do that update there as well. I am not sure if it was the right thing to do but just as a start i hard-coded an update to the ArticleCategory table, just after I do the UpdateModel. This works but I am not sure how to code this update?
I am using the repository patter and i somehow feel that I should be passing an Article and an ArticleCategory object from the view to the controller? While I was writing this I thought that I could just extend my article object to include the categoryID but what if I really wanted to pass two un-related objects from the view to the controller? The UpdateModel persistes the database objects as by VoodooMagic, how would it work if I wanted to update 2 un-related objects?
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Nov 2, 2010
I am new to entity framework , it is really very good , but I want to know what is the difference between using entity framework with stored procedure or without stored procedure , which one the faster and what is the benefits for using stored procedures with entity framework.
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Jun 30, 2010
I have an EDM, it includes the entities extension and history. My goal is to use history to keep track of all the changes made to extension entity. For example, if extension with ID 223 has its property 'Name_Display' changed - I want the history entity to record this.
I'm using ASP.NET with VB.NET. Where in my code do I put the hook to say, "update the history entity" and what should that hook look like?
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Mar 3, 2011
I'm working on a MVC3 application and I created my POCO classes from my database with the DbContext Code Generator. All goes fine until I got stuck in this situation. Note that I use the repository pattern and I use for every entity a dedicated repository that every get a new instance of the DbContext.
Now, I'm in this situation:
object A has a relation one-to-many with B (A can have one or many B)
object B has a relation many-to-one with C (C can have one or many B)
object B has a relation many-to-one with D (D can have one or many B)
I should add a new object B, consider that object C and D are yet existing, so I must only do the relation and the object A can be created or updated. In the specific consider that A is customer and B is subscriptions (C and D are virtual objects properties
in the B).Now If I try to save I got duplicates in C and D tables, while the management of the object seems to work.
Here's the code: [Code]....
And here the add and the save method of the customer repository: [Code]....
Should I check for every relation and modify the state of the entry to Unchanged or something like that ?
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Feb 9, 2011
I get an cast exception when i am trying to insert an entity in Entity Framework (using code-first). From this code :
public virtual T Insert(T entity)
{
return Context.Set<T>().Add(entity);
}
The cast exception is like "impossible to cast ...Collection'1(Entity) to type (Entity)" I can't figure out why. I am pretty sure ive done everything right. Post entity
public class Post
{
public long PostId { get; private set; }
public DateTime date { get; set; }
[Required]
public string Subject { get; set; }
public User User { get; set; }
public Category Category { get; set; }
[Required]
public string Body { get; set; }
public virtual ICollection<Tag> Tags { get; private set; }
public Post()
{
Category = new Category();
if (Tags == null)
Tags = new Collection<Tag>();
}................................
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Feb 10, 2011
I am mapping a stored procedure to an entity by right clicking on the entity (in the .edmx) and selecting "Stored Procedure Mapping." This brings you to a Mapping Details - "Name of Entity" Window that allows you to select the insert, update, and delete stored procedures associated with the Entity. It also maps the stored procedure parameter to the Entity "Property" (Column).
I'm gettin an error "error 2042: Parameter Mapping specified is not valid." The cause of the error is fairly obvious, in the Insert stored procedure that has been selected, a 'CHAR' parameter is being mapped to an Int32 Entity Property. I altered the stored procedure parameter to match the entity, I deleted the stored procedure, readded, and reslected it as the Insert function. I also cleaned, validated, updated model from database. No matter what I do, the parameter list in the mapping details doesn't reflect the change to the stored procedure. It's stuck on a char --> int32 mapping, even though it has been changed, like it's buried deep in meta data some where.
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Mar 31, 2011
I have a stupid problem with the Entity Framework. I get the following Exception:
[Code]....
I have an entity with a 4 fields representing the primary key. I copy it via serialization (works fine). I set the old entity to not valid (Datefield set to a date in the past, this field is part of the PK) and set the copied entity to DateTime.Now.Date. When I call context.AddObject I get the Exception above. I tried copying the entity via reflection but the entity has 3-4 references. And when copied, I get another Exception before even Adding the entity to the context. I also tried setting newObj.EntityKey = null and reset all the fields neccessary for the PK. I just want a whole copy of an entity with a different primary key (and some other fields changed too) and Create it in the database.
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Sep 21, 2010
I'm writing a custom .NET MembershipProvider (not the built in one) and trying to update using Entity Framework. But of course i have no access to (Try)UpdateModel. How can i update it?
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Jan 5, 2011
I have an Events table and an InstallmentPlans table. The relationship is 0..1 : an Event can have 0 or 1 Installment plans. If I want to remove the existing InstallmentPlan for an event, how do I do this? Setting it to null doesn't seem to work:
_event.InstallmentPlan = null;
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Feb 3, 2011
Here's a simple code snippet where I create a new Entity object and call SaveChanges() to create a new record in the mapped database table.
[Code]....
What I'm trying to figure out is whether there is a way to derive this new key for my entity, e, from the ObjectContext, m? The reason for this is that the way my actual code is structured, my entity object is already out of scope at the point where I call the SaveChanges() method.
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Sep 24, 2010
I am trying to do something like this:
[Code]....
But ofcourse it is not working as I want to. The Ordering works on Question.Order, but I would also the
Questions.SubQuestions List to be ordered according to SubQuestions.Order
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Jun 15, 2010
I am using entity framework. My model has entity tblGameInfo where in navigation properties are associations called tblPlayer1 and tblPlayer2 which links to entity tblPlayer. I have listview on my page where I want to show game info with players names. I have found that in of listview I should have e.g. one of those:
[Code]....
But it does not work. I got nothing displayed in a listview. I have tried many different options but cannot find working one. Probably is some simple mistake but I am new to asp.net and cannot find it. Second problem with this is editing. In edit template there is dropdownlist with all players.
[Code]....
How do I databind it? It is not allowed to bind and change properties? It writes me that element does not exist on a list of elements.
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