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• Which .NET data provider?

  - by worlds-apart89

  I am new to database programming, so I'd like help getting on the right track. I have read that there are Microsoft-defined and third-party data providers for data access. MSDN has information on data providers for SQL Server, OLE DB, ODBC, Oracle, as well as the EntityClient provider (Entity Framework). Which data provider is today's hottest, most-widely used model? Which one is the future? Also, I have seen Linq to SQL tutorials, but what category does L2S fall into?

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• Best way to attach row from datagrid to EF.

  - by AKoran

  Using MVVM and EF...I have a datagrid binding to a View Model (using ObservableCollection). The view model has a save command which simply calls the SaveChanges command of the Data Context. However, when a user adds a new row to the datagrid, the new entity is detached. Is there any easy way to automatically attach it when it gets created. Currently, I'm having to do this in the Save command of my View Model and it seems a bit clunky: foreach (var dataItem in _DataList) // where _DataList is the ObservableCollection { if (dataItem.EntityState == EntityState.Detached) { _DataContext.AddToTestTables(dataItem); } } _DataContext.SaveChanges();

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• iPhone - Create not persistant entities in core data

  - by ncohen

  Hi everyone, I would like to use entity objects but not store them... I read that I could create them like this: myElement = (Element *)[NSEntityDescription insertNewObjectForEntityForName:@"Element" inManagedObjectContext:managedObjectContext]; And right after that remove them: [managedObjectContext deleteObject:myElement]; then I can use my elements: myElement.property1 = @"Hello"; This works pretty well even though I think this is probably not the most optimal way to do it... Then I try to use it in my UITableView... the problem is that the object get released after the initialization. My table becomes empty when I move it! Thanks

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• Mocking a namespace in a partial class.

  - by Nix

  I am messing around with Entity Framework 3.5 SP1 and I am trying to find a cleaner way to do the below. Basically I have an EF model and I am adding some Eager Loaded entities and i want to put them in the partial class context Eager namespace. Currently I am using composition but I feel like there is an easier way to do what I want. namespace Entities{ public partial class TestObjectContext { EagerExtensions Eager { get;set;} public TestObjectContext(){ Eager = new EagerExtensions (this); } } public partial class EagerExtensions { TestObjectContext context; public EagerExtensions(TestObjectContext _context){ context = _context; } public IQueryable<TestEntity> TestEntity { get { return context.TestEntity .Include("TestEntityType") .Include("Test.Attached.AttachedType") .AsQueryable(); } } } } public class Tester{ public void ShowHowIWantIt(){ TestObjectContext context= new TestObjectContext(); var query = from a in context.Eager.TestEntity select a; } }

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• LINQ query for tag system: Matching any of several tags?

  - by David Veeneman

  I am just getting started with LINQ. I am creating an Entity Framework app that uses the canonical Post and Tag model. A Post contains an ID, Text, and Tags, and a Tag contains an ID, a Name, and Posts. A previous thread on StackOverflow showed me how to query for a Post that matches all Tag objects (A and B and C) in a search list. But how would I query for a Post that matches any Tag (A or B or C) in the list? Thanks for your help.

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• ASP.NET GridView throwing error: "Update is disabled for this control".

  - by NTDLS

  I have the absolutely most simple setup imaginable. A single table defined in an Entity model in ASP.net v4, the model is bound directly to a GridView with AutoGenerateEditButton enabled. However, each time I hit edit, then save, the page throws the error “Update is disabled for this control" for which I cannot find a solution. What is causing this error? What can do to resolve it? <% <asp:GridView ID="MenuItemsGrid" runat="server" DataSourceID="gridDataSource" AutoGenerateEditButton="true" AutoGenerateColumns="true"> </asp:GridView> <asp:EntityDataSource ID="gridDataSource" runat="server" ConnectionString="name=dataEntitiesModel" DefaultContainerName="dataEntities" EntitySetName="MenuItems" /> %>

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• Include in enity framework 4

  - by molgan

  Hello I've been using enity framework that came with 3.5sp. And now I've redone things for enityframework 4 and asp.net mvc 2. I've come across something (which worked in my previous version and asp.net mvc 1.0). I have this: public IQueryable<Booking> GetBookings() { return from b in _entities.Bookings.Include("BookingObject") select b; } And in my controller I have: return View("Index", new BookingsViewModel { Bookings = _br.GetBookings().ByDay(DateTime.Today) }); And it doesnt seem to include the "BookingObject"-entity, so I can type like <%= Model.Bookings.BookingObject.BookingObjectName %> in my view. What might be missing here? Do I need to turn something on in the diagram for it to include entities or? /M

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• Can you automatically remove characters from entities created?

  - by JamesStuddart

  Hi, In my sql database I have tables with name which include underscores, for readability. Just to try and make it clearer see below: TableFoo TableFoo_TableBah Where TableFoo has a key linking to TableFoo_TableBah, this is done so you can quickly see what the table TableBah relates to. I have used this naming convention before with tools such as CodeSmith which give the option to remove the underscores, but I cannot see how to do this in Entity Framework 4. Is there a way to do this, or am I stuck with either renaming my tables or having objets such as TableFoo_TableBah? Thanks,

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• Unique number identifier generation

  - by xwrs

  I have to create logic for generation unique number identifier for records in database. id, generated in database is a separate column. At this moment, when user calls "create record" action, I save new record, get its database id, generate record number using this id, then put it to the edit form. Using this way means that all entity fields should be nullable to save record to database. I don't like this way. I know that should be better way. Is there a better practice to generate unique number identifier? What is possibility of generating non-unique random numbers? Thank you

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• Custom DDL Templates for Visual Studio 2010

  - by Stacey

  I was wondering if anyone knows of some good community distributed custom DDL templates for Entity Framework 4.0. The default DDL to SQL10 Works well enough, but we're looking to do some customization to the naming convention that it just isn't offering us. I'm not really finding many samples out there of people doing this, so I was hoping someone might know of a resource I'm overlooking (perhaps I am searching for it wrong, or misunderstanding how the whole process works) Specifically we're wanting to change up how it writes out fields from relationships. For instance, the default template puts in.. tablename_propertyendpoint_propertyname. We're wanting to find tune this to our naming scheme a little more. And none of us can quite figure out where in the .tt files it is doing this exact behavior.

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• EF Stored Procedure Complex Type

  - by Web Dev

  I am using EF4. I am somewhat confused on on the Entity Framework Complex name. When I go to Functional Import of a Stored Procedure name and it ask me to type in the Complex name, is that supposed to be the name of of a class that can handle that output. For examle, say if my stored procedure returns FirstName, LastName. Is the Complex name supposed to be a class that can handle that output in this case PersonName? public class PersonName { public string FirstName {get; set;} public string LastName {get;set} }

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• Time for creation of database on site

  - by slo2ols

  Hi. When and where would you create database to develop web site using ASP.NET MVC 2 and Entity Framework 4 (CreateDatabase method). I think about first run of web site and redirect on welcome page, when controller creates database from model. But I doubt about details: 1. Where? In HttpModule, but request of any image or css will check that database exist. In custom RouteHandler, but then anybody need to know that need to use this handler when to add route. In BaseController, but then code will look like SomeController(..., IDatabase database) : base(database). 2. When? Better create database on first run by any url or may be on deployment of site (additional tool which create ObjectContext and invoke CreateDatabase)? Thanks.

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• Nhibernate fires SQL commands

  - by Chris

  Hi all, when updating an entity A, NHibernate also send an SQL update command for some other entity B. A and B are not related. Just before saving entity A, the parent of entity B is loaded via a SQLQuery. Then, when accessed, B is lazy loaded (part of a collection). If I save entity A an update statement for entity B is generated as well. How can that be, that when saving an entity, another entity loaded before but is not related to the entity saved, is updated as well?! Can I somehow track where the update comes from? Btw. I am using an save event listener. Could it be that this is always triggered for entity loaded, even though they are not saved explicitly? public class EntitySaveEventListener : NHibernate.Event.Default.DefaultSaveEventListener { protected override object PerformSaveOrUpdate(SaveOrUpdateEvent e) { //auditing return base.PerformSaveOrUpdate(e); } } Update (sorry for providing not enough info): I tracked it down a bit. A select stateement on a entity called address is executed (is it lazy loaded by a parent). Then I create a new entity called Request. Right before saving this entity a session flush is called which updates the address, even though I did not call save or update on the address. Address is a collection within Request. <class name="Request" table="Request"> <bag name="addresses" access="field" cascade="all-delete-orphan" where="IsDeleted = 0"> <key column="RequestId"/> <one-to-many class="Address"/> </bag> ... // address is fetched only NHibernate.SQL: 2010-02-17 11:47:21,306 [21] DEBUG NHibernate.SQL [(null)] - SELECT addresses0_.RequestId as ServiceP8_3_, .... // session flushed here // address is updated NHibernate.SQL: 2010-02-17 11:47:34,306 [21] DEBUG NHibernate.SQL [(null)] - Batch commands: command 0:UPDATE Address SET Street = @p0, ..... Would the address be updated automatically when it is manipulated somehow even though it is not explicitly saved via it's parent (cascade)?

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• Explicit casting doesn't work in default model binding

  - by Felix

  I am using ASP.NET MVC2 and Entity Framework. I am going to simplify the situation a little; hopefully it will make it clearer, not more confusing! I have a controller action to create address, and the country is a lookup table (in other words, there is a one-to-many relationship between Country and Address classes). Let's say for clarity that the field in the Address class is called Address.Land. And, for the purposes of the dropdown list, I am getting Country.CountryID and Country.Name. I am aware of Model vs. Input validation. So, if I call the dropdown field formLand - I can make it work. But if I call the field Land (that is, matching the variable in Address class) - I am getting the following error: "The parameter conversion from type 'System.String' to type 'App.Country' failed because no type converter can convert between these types." OK, this makes sense. A string (CountryID) comes from the form and the binder doesn't know how to convert it to Country type. So, I wrote the converter: namespace App { public partial class Country { public static explicit operator Country(string countryID) { AppEntities context = new AppEntities(); Country country = (Country) context.GetObjectByKey( new EntityKey("AppEntities.Countries", "CountryID", countryID)); return country; } } } FWIW, I tried both explicit and implicit. I tested it from the controller - Country c = (Country)"fr" - and it works fine. However, it never got invoked when the View is posted. I am getting the same "no type converter" error in the model. Any ideas how to hint to the model binder that there is a type converter? Thanks

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• EF4 querying from parent to grandchildren

  - by Hans Kesting

  I have a model withs Parents, Children and Grandchildren, in a many-to-many relationship. Using this article I created POCO classes that work fine, except for one thing I can't yet figure out. When I query the Parents or Children directly using LINQ, the SQL reflects the LINQ query (a .Count() executes a COUNT in the database and so on) - fine. The Parent class has a Children property, to access it's children. But (and now for the problem) this doesn't expose an IQueryable interface but an ICollection. So when I access the Children property on a particular parent all the Parent's Children are read. Even worse, when I access the Grandchildren (theParent.Children.SelectMany(child => child.GrandChildren).Count()) then for each and every child a separate request is issued to select all data of it's grandchildren. That's a lot of separate queries! Changing the type of the Children property from ICollection to IQueryable doesn't solve this. Apart from missing methods I need, like Add() and Remove(), EF just doesn't recognize the navigation property then. Are there correct ways (as in: low database interaction) of querying through children (and what are they)? Or is this just not possible?

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• TypeConverter prevents ApplyPropertyChanges in EntityFramework

  - by Felix

  I ran into an interesting problem (hopefully, interesting not just for me :) I am running Entity Framework 1 (.NET 3.5) and ASP.NET MVC 2. I have a Customer class that has many-to-one relationship with Country class (in other words, Country is a lookup table for customers - I described more in this post: http://stackoverflow.com/questions/2404801/explicit-casting-doesnt-work-in-default-model-binding ) I got TypeConverter to work; so I am getting a perfect object into controller's Post method. Create works fine; however, in Edit I am getting the following error when I call ApplyPropertyChanges: The existing object in the ObjectContext is in the Added state. Changes can only be applied when the existing object is in an unchanged or modified state. The controller code is fairly trivial: public ActionResult Edit(Customer customerToEdit) { if (ModelState.IsValid) { Customer cust = (Customer)context.GetObjectByKey( new EntityKey("BAEntities.Customers", "CustomerID", customerToEdit.CustomerID)); context.ApplyPropertyChanges(cust.EntityKey.EntitySetName, customerToEdit); context.SaveChanges(); } return View(...); } If I remove country from the form, it works fine; and if I assign dropdown value to EntityReference "manually" - it works as well. TypeConverter code is also fairly simple, but I've never used TypeConverter before, so I may be missing something here: public override object ConvertFrom(ITypeDescriptorContext typeContext, CultureInfo culture, object value) { if (value is string) { int countryID = Int16.Parse((string)value); Country country = (Country)context.GetObjectByKey( new EntityKey("BAEntities.Countries", "CountryID", countryID)); return country; } return base.ConvertFrom(typeContext, culture, value); }

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• When are SQL views appropriate in ASP.net MVC?

  - by sslepian

  I've got a table called Protocol, a table called Eligibility, and a Protocol_Eligibilty table that maps the two together (a many to many relationship). If I wanted to make a perfect copy of an entry in the Protocol table, and create all the needed mappings in the Protocol_Eligibility table, would using an SQL view be helpful, from a performance standpoint? Protocol will have around 1000 rows, Eligibility will have about 200, and I expect each Protocol to map to about 10 Eligibility rows and each Eligibility to map to over 100 rows in Protocol. Here's how I'm doing this with the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility_View where pel.pid == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = (from pel in _documentDataModel.Eligibility where pel.ID == pel_item.eid select pel).First(); newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); } And this is without the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility where pel.Protocol.ID == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { pel_item.EligibilityReference.Load(); newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = pel_item.Eligibility; newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); }

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• EF 6 Code First Many to many With Payload and self referencing many to many

  - by lesley86

  I Have the problem where i have a many to many relationship and on one of the tables there will be a self referencing many to many. So basically a school have zero or many groups and many groups can have 0 or many schools. The groups table will contain a parent child many to many with itself because a group can be a child of another group or it can have no children and that child can have a child, one child can also have many parents or a entity can have no parents. I created a mapping table with Payload to solvethe first many to many problem. code snippet public class School { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroupMap { public virtual School School public virtual SchoolGroup SchoolGroup } i Then tried modifying the code the following way for the the self referencing many to many public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps public virtual ICollection<SchoolGroup> Parents public virtual ICollection<SchoolGroup> Children } I changed the context with has many and an auto mapping table (forgive me i have been trying so many things today i do not have the exact code). I received an error the properties on the classes must match. Can anyone help please. I want to do create navigation properties on the self referencing many to many. Also a seed example would be appreciated regards

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• Linq to Entities custom ordering via position mapping table

  - by Bigfellahull

  Hi, I have a news table and I would like to implement custom ordering. I have done this before via a positional mapping table which has newsIds and a position. I then LEFT OUTER JOIN the position table ON news.newsId = position.itemId with a select case statement CASE WHEN [position] IS NULL THEN 9999 ELSE [position] END and order by position asc, articleDate desc. Now I am trying to do the same with Linq to Entities. I have set up my tables with a PK, FK relationship so that my News object has an Entity Collection of positions. Now comes the bit I can't work out. How to implement the LEFT OUTER JOIN. I have so far: var query = SelectMany (n => n.Positions, (n, s) => new { n, s }) .OrderBy(x => x.s.position) .ThenByDescending(x => x.n.articleDate) .Select(x => x.n); This kinda works. However this uses a INNER JOIN so not what I am after. I had another idea: ret = ret.OrderBy(n => n.ShufflePositions.Select(s => s.position)); However I get the error DbSortClause expressions must have a type that is order comparable. I also tried ret = ret.GroupJoin(tse.ShufflePositions, n => n.id, s => s.itemId, (n, s) => new { n, s }) .OrderBy(x => x.s.Select(z => z.position)) .ThenByDescending(x => x.n.articleDate) .Select(x => x.n); but I get the same error! If anyone can help me out, it would be much appreciated!

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• Association Mapping Details confusion?

  - by AaronLS

  I have never understood why the associations in EntityFramework look the way they do in the Mapping Details window. When I select the line between 2 tables for an association, for example FK_ApplicationSectionsNodes_FormItems, it shows this: Association Maps to ApplicationSectionNodes FormItems (key symbol) FormItemId:Int32 <--> FormItemId:int ApplicationSectionNodes (key symbol) NodeId:Int32 <--> (key symbol) NodeId : int Fortunately this one was create automatically for me based on the foreign key constraints in my database, but whenever no constraints exist, I have a hard to creating associations manually(when the database doesn't have a diagram setup) because I don't understand the mapping details for associations. FormItems table has a primary key identity column FormItemId, and ApplicationSectionNodes contains a FormItemId column that is the foreign key and has NodeId as a primary key identity column. What really makes no sense to me is why the association has anything listed about the NodeId, when NodeId doesn't have anything to do with the foreign key relationship? (It's even more confusing with self referencing relationships, but maybe if I could understand the above case I'd have a better handle). CREATE TABLE [dbo].[ApplicationSectionNodes]( [NodeID] [int] IDENTITY(1,1) NOT NULL, [OutlineText] [varchar](5000) NULL, [ParentNodeID] [int] NULL, [FormItemId] [int] NULL, CONSTRAINT [PK_ApplicationSectionNodes] PRIMARY KEY CLUSTERED ( [NodeID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY], CONSTRAINT [UQ_ApplicationSectionNodesFormItemId] UNIQUE NONCLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] FOREIGN KEY([ParentNodeID]) REFERENCES [dbo].[ApplicationSectionNodes] ([NodeID]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_FormItems] FOREIGN KEY([FormItemId]) REFERENCES [dbo].[FormItems] ([FormItemId]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_FormItems] GO FormItems Table: CREATE TABLE [dbo].[FormItems]( [FormItemId] [int] IDENTITY(1,1) NOT NULL, [FormItemType] [int] NULL, CONSTRAINT [PK_FormItems] PRIMARY KEY CLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[FormItems] WITH NOCHECK ADD CONSTRAINT [FK_FormItems_FormItemTypes] FOREIGN KEY([FormItemType]) REFERENCES [dbo].[FormItemTypes] ([FormItemTypeId]) GO ALTER TABLE [dbo].[FormItems] NOCHECK CONSTRAINT [FK_FormItems_FormItemTypes] GO

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• Beginner Question on traversing a EF4 model

  - by user564577

  I have a basic EF4 model with two entities. I'm using Self Tracking Entities Client has ClientAddresses relationship on clientkey = clientkey. (1 to many) How do i get a list/collection of client entities (STE) and their addresses (STE) but only ones where they live in a particular state or some such filter on the address??? This seems to filter and bring back clients but doesnt bring back addresses. var j = from client in context.Clients where client.ClientAddresses.All(c => c.ZIP == "80923") select client; I cant get this to create the Addresses because ClientAddresses is IEnumerable and it needs a TrackableCollection var query = from t1 in context.Clients join t2 in context.ClientAddresses on t1.ClientKey equals t2.ClientKey where t2.ZIP == "80923" select new Client { FirstName = t1.FirstName, LastName = t1.LastName, IsEnabled = t1.IsEnabled, ClientKey = t1.ClientKey, ChangeUser = t1.ChangeUser, ChangeDate = t1.ChangeDate, ClientAddresses = from a in t1.ClientAddresses select new ClientAddress { AddressKey = a.AddressKey, AddressLine1 = a.AddressLine1, AddressLine2 = a.AddressLine2, AddressTypeCode = a.AddressTypeCode, City = a.City, ClientKey = a.ClientKey, State = a.State, ZIP = a.ZIP } }; Any pointers would be appreciated. Thanks Edit: This seems to work.... var j = from client in context.Clients.Include("ClientAddresses") where client.ClientAddresses.Any(c => c.ZIP == "80923") select client;

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• EF Code First - Relationships

  - by CaffGeek

  I have these classes public class EntityBase : IEntity { public int Id { get; set; } public DateTime Created { get; set; } public string CreatedBy { get; set; } public DateTime Updated { get; set; } public string UpdatedBy { get; set; } } public class EftInterface : EntityBase { public string Name { get; set; } public Provider Provider { get; set; } public List<BusinessUnit> BusinessUnits { get; set; } } public class Provider : EntityBase, IEntity { public string Name { get; set; } public decimal DefaultDebitLimit { get; set; } public decimal DefaultCreditLimit { get; set; } public decimal TreasuryDebitLimit { get; set; } public decimal TreasuryCreditLimit { get; set; } } public class BusinessUnit : EntityBase { public string Name { get; set; } } An interface, is really a Provider, with a collection of Business Units. The issue is that while my db model ends up having a correct EftInterfaces table, with a FK to Provider_Id, the BusinessUnits table has a FK to EftInterface_Id. But, a BusinessUnit can be included in more than one EftInterface. I need a many to many relationship. A BusinessUnit can be part of many EftInterfaces, and an EftInterface can contain many BusinessUnits. How can I get CodeFirst to generate the many-to-many table?

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• IEnumerator seems to be effecting all objects, and not one at a time

  - by PFranchise

  Hey, I am trying to alter an attribute of an object. I am setting it to the value of that same attribute stored on another table. There is a one to many relationship between the two. The product end is the one and the versions is the many. Right now, both these methods that I have tried have set all the products returned equal to the final version object. So, in this case they are all the same. I am not sure where the issue lies. Here are my two code snipets, both yield the same result. int x = 1 IEnumerator<Product> ie = productQuery.GetEnumerator(); while (ie.MoveNext()) { ie.Current.RSTATE = ie.Current.Versions.First(o => o.VersionNumber == x).RSTATE; x++; } and foreach (var product in productQuery) { product.RSTATE = product.Versions.Single(o => o.VersionNumber == x).RSTATE; x++; } The versions table holds information for previous products, each is distinguished by the version number. I know that it will start at 1 and go until it reaches the current version, based on my query returning the proper number of products. Thanks for any advice.

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• EF4 querying through the generations

  - by Hans Kesting

  I have a model withs Parents, Children and Grandchildren, in a many-to-many relationship. Using this article I created POCO classes that work fine, except for one thing I can't yet figure out. When I query the Parents or Children directly using LINQ, the SQL reflects the LINQ query (a .Count() executes a COUNT in the database and so on) - fine. The Parent class has a Children property, to access it's children. But (and now for the problem) this doesn't expose an IQueryable interface but an ICollection. So when I access the Children property on a particular parent all the Parent's Children are read. Even worse, when I access the Grandchildren (theParent.Children.SelectMany(child => child.GrandChildren).Count()) then for each and every child a separate request is issued to select it's grandchildren. Changing the type of the Children property from ICollection to IQueryable doesn't solve this. Apart from missing needed methods like Add() and Remove(), EF just doesn't recognize the property then. Are there correct ways (as in: low database interaction) of querying through children (and what are they)? Or is this just not possible?

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• How can I use UML to model a relationship between two classes, where one has functions exposed as friend to the other?

  - by user1796528

  I have a two classes: ------------ --------------- X Y ------------ --------------- relation ------------ ------------------ --------------- A() C() B() D() E() ------------ --------------- I want to inherit just these two functions from X class, where they are defined with the friend access modifier. My class will be: --------------- Y --------------- --------------- C() A() D() --------------- Y class uses some functions of X class namely A and D. How can I model this relationship in a UML class diagram?

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