Questions tagged [entity-framework]

Entity Framework is a LINQ-based object-database mapper for .NET. It supports change tracking, updates, and schema migrations for many databases. Please add a version-specific tag as well.

Entity Framework is .NET's Object-Relational Mapping (ORM) tool that enables .NET developers to work with relational data using domain-specific objects. It eliminates the need for most of the data-access code that developers usually need to write. Either natively, or through third-party libraries, it supports most major RDBM products including SQL Server, MySQL, Oracle, PostgreSQL and SQLite. It also supports Microsoft's "LINQ" syntax and lambda-expressions.

Entity Framework was first developed for .Net framework (production-ready versions 4.x - 6.x). In 2016, Entity Framework for .Net core (EF-core) was introduced, having a completely new codebase which shares many concepts with the classic framework but differs considerably in mapping syntax, query translation and specific features. After version 1 and 2, EF-core 3 came with many breaking changes, marking the beginning of a more stable evolution path. EF core 5 (versions keep track with .Net core versions) has far less breaking changes.

As of version 6.3.0, EF 6 is cross-platform. It targets .Net standard 2.1. NuGet packages are available for .Net core 3 and .NET Framework 4.x.

Because of all these different versions it's very important to use the right tags when asking questions.

Entity Framework is well-documented.

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Validation failed for one or more entities while saving changes to SQL Server Database using Entity Framework

I want to save my Edit to Database and I am using Entity FrameWork Code-First in ASP.NET MVC 3 / C# but I am getting errors. In my Event class, I have DateTime and TimeSpan datatypes but in my database, I've got Date and time respectively. Could…
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Entity Framework: There is already an open DataReader associated with this Command

I am using Entity Framework and occasionally i will get this error. EntityCommandExecutionException {"There is already an open DataReader associated with this Command which must be closed first."} at…
Sonic Soul
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What difference does .AsNoTracking() make?

I have a question regarding the .AsNoTracking() extension, as this is all quite new and quite confusing. I'm using a per-request context for a website. A lot of my entities don't change so don't need to be tracked, but I have the following scenario…
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Create code first, many to many, with additional fields in association table

I have this scenario: public class Member { public int MemberID { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public virtual ICollection Comments { get; set; } } public class…
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How to update record using Entity Framework 6?

I am trying to update a record using EF6. First finding the record, if it exists, update. Here is my code: var book = new Model.Book { BookNumber = _book.BookNumber, BookName = _book.BookName, BookTitle = _book.BookTitle, }; using (var…
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Entity Framework Code First - two Foreign Keys from same table

I've just started using EF code first, so I'm a total beginner in this topic. I wanted to create relations between Teams and Matches: 1 match = 2 teams (home, guest) and result. I thought it's easy to create such a model, so I started…
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Unique Key constraints for multiple columns in Entity Framework

I'm using Entity Framework 5.0 Code First; public class Entity { [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)] public string EntityId { get; set;} public int FirstColumn { get; set;} public int SecondColumn { get; set;} …
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Entity Framework Core add unique constraint code-first

I can't find way to add a unique constraint to my field with using attribute: public class User { [Required] public int Id { get; set; } [Required] // [Index("IX_FirstAndSecond", 2, IsUnique = true)] not supported by core public…
Vadim M
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How to call Stored Procedure in Entity Framework 6 (Code-First)?

I am very new to Entity Framework 6 and I want to implement stored procedures in my project. I have a stored procedure as follows: ALTER PROCEDURE [dbo].[insert_department] @Name [varchar](100) AS BEGIN INSERT [dbo].[Departments]([Name]) …
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Non-static method requires a target

I have a controller action that works fine on Firefox both locally and in production, and IE locally, but not IE in production. Here is my controller action: public ActionResult MNPurchase() { CalculationViewModel calculationViewModel =…
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Should services always return DTOs, or can they also return domain models?

I'm (re)designing large-scale application, we use multi-layer architecture based on DDD. We have MVC with data layer (implementation of repositories), domain layer (definition of domain model and interfaces - repositories, services, unit of work),…
19 answers

Decimal precision and scale in EF Code First

I'm experimenting with this code-first approach, but I'm find out now that a property of type System.Decimal gets mapped to a sql column of type decimal(18, 0). How do I set the precision of the database column?
Dave Van den Eynde
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What does principal end of an association means in 1:1 relationship in Entity framework

public class Foo { public string FooId{get;set;} public Boo Boo{get;set;} } public class Boo { public string BooId{get;set;} public Foo Foo{get;set;} } I was trying to do this in Entity Framework when I got the error: Unable to…
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Entity Framework and Connection Pooling

I've recently started to use the Entity Framework 4.0 in my .NET 4.0 application and am curious about a few things relating to pooling. Connection pooling as I know is managed by the ADO.NET data provider, in my case that of MS SQL server. Does…
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Entity Framework: One Database, Multiple DbContexts. Is this a bad idea?

My impression to date has been that a DbContext is meant to represent your database, and thus, if your application uses one database, you'd want only one DbContext. However, some colleagues want to break functional areas out into separate DbContext…